The document presents the design of an integrated rainwater collection, storage and filtration system for households in the Mekong Delta of Vietnam. It describes the design of each subsystem, including a bamboo gutters system, a ferrocement storage tank, and a clay pot filtration unit. An analysis is provided of each design to meet requirements for affordability, effectiveness, and ability to be constructed with local materials and unskilled labor.

1. DURHAM UNIVERSITY
School of Engineering and
Computing Sciences
Level 2 Design
Feasibility Report on Rainwater Storage
and
Filtration in the Mekong Delta
Mission Statement: To design and provide a water collection, storage
and filtration system that is both affordable and effective for a
household in the Mekong Delta.
Authors: Kevin De Michelis, Charles Heard, Tom Pallister, Nick Sidwell,
Callum Stephen, Xaver Touschek
Supervisors: John Garside and Peter Waugh
Group 17.

2. 1
Executive Summary
The objective of this project is to design and provide a water collection, storage and filtration system
that is both affordable and effective for a household in the Mekong Delta.
The Mekong Delta is an agricultural region in the south of Vietnam that experiences an annual rain
cycle consisting of a dry and wet season each of which lasts roughly 6 months. The average farmer
has a family of four and lives in a commune with a salary of less than $10 per day. This region is
difficult to access due to poor infrastructure and can mainly be reached by using the many rivers and
canals.
Currently, drinking water is collected from three sources: rainwater, borehole water, and surface
water. This water is typically stored in open cement or ceramic jars during the wet season. However,
this barely provides a family with enough water to last the dry season. Furthermore there is often a
build-up of impurities in their storage jars that leads to water contamination. There is also a lack of
adequate filtration which can cause severe water borne diseases and infections.
A domestic system that harvests rainwater was concluded as the most appropriate solution for the
Mekong Delta. A central communal water filtration plant had no way to distribute water due to a
lack of piping infrastructure and rainwater was deemed as the cleanest and most plentiful option.
The domestic approach means having to provide the knowledge and designs of the system to the
average farmer. Therefore the solution took into account locally sourced materials and local
businesses as well as providing clear and concise instructions for construction.
To make the process clear the solution was divided into three parts:
A more detailed and quantified user requirement specification table has been written up in the
main report for each section. However, these are the decisive factors that stood out:
Collection Storage Filtration
System User Requirement Specification
Collection Collection of 4m3
in 2 months.
Must allow water to be diverted away from tank to wash the roof.
Storage Removal of any initial contaminants.
Storage of 3600 litres.
Prevents sunlight access.
Costs less than $80.
Can be built by unskilled labourer.
Exit flow rate of 7.5 litres/min.
Filtration Filters > 90% of organic material.
No operational costs.
Flow rate > 3litres/person per day.
Costs less than $10.

3. 2
Collection:
Guttering System Final Design Key Physical aspects
Simple open gutters between roof and tank.
Removable section to allow water to be diverted
away from tank.
Both gutters and supports made of bamboo.
Functionality
Fully capable of filling the tank during the wet
season (several times over)
Allows siphoning of water where required (eg to
clean the roof) by the removable section.
Very easy for anyone to erect, maintain, and
repair.
Total cost: $8.88
Storage:
Storage Tank Final Design Key Physical aspects
Built using ferrocement.
Bowl beneath tap to allow for water access.
Overflow pipe at top of tank.
Wash out pipe at bottom of tank.
Collection hole on sloped roof.
Inlet filter at entrance to tank
Functionality
Stores 3,600 litres of water; enough to last a
family of four through the six month dry season.
Does not allow exposure to sunlight.
It is robust enough to withstand flooding.
Construction time is under 2 weeks.
Instruction manual allows the tank to be built by
an unskilled labourer.
Can safely withstand internal hydrostatic
pressures at full capacity.
Water access has flow rate over 7.5 litres/minute
Tank can be easily maintained by an unskilled
labourer
Initial filtration unit at the top avoids debris and
insects from entering the tank.
Total cost: $65.38

4. 3
Filtration:
Filtration System Final Design Key Physical aspects
Clay pot filter running into plastic water butt
Ceramic pot is made from a 3:1 clay: rice husk mix
System is 660mm tall and 500mm wide
Plastic Butt is wider at the bottom for increased
stability
Water is cleaned by physical straining and
chemical action
Functionality
Filters 3L of water per hour
Removes over 90% of bacteria
Reduces water turbidity to under 5%
Has zero power requirements
Only requires cleaning once a month
Very affordable at only $8.10
$8.10
Total cost:
The layout of each household in the Mekong Delta will inevitably differ from one another. However,
the design and implementation of each section within the project has allowed for greater
adaptability. The guttering system is fully adjustable to any roof dimensions whilst also providing
initial filtration. The storage tank can be positioned where ever the user desires it to be and has the
potential to be connected to the household via water piping. The filtration unit is easily portable and
unobtrusive within the home.
The collection, storage, and filtration designs have all successfully fulfilled their respective user
requirement specifications. Therefore this integrated system is the optimum rainwater storage and
filtration solution available to the people of the Mekong Delta.

5. 4
Table of Contents
Executive Summary.................................................................................................................................1
Collection: ...........................................................................................................................................2
Storage:...............................................................................................................................................2
Filtration:.............................................................................................................................................3
Team Assignment Overview ...................................................................................................................9
1. Introduction ......................................................................................................................................10
1.1 Project Statement.......................................................................................................................10
1.2 Mekong Delta..............................................................................................................................10
1.3 Current Practice ..........................................................................................................................10
1.4 Approach and Philosophy ...........................................................................................................11
1.5 Project Management ..................................................................................................................12
1.5.1 Planning................................................................................................................................12
1.5.2 URS and feasibility report ....................................................................................................12
1.5.3 Teamwork ............................................................................................................................12
Charlie Heard & Kevin De Michelis .......................................................................................................13
2. Collection ..........................................................................................................................................14
2.1 Water sources.............................................................................................................................14
2.2 Concept developments...............................................................................................................15
2.3 Final design .................................................................................................................................16
2.3.1 Attaching to the roof............................................................................................................16
2.3.2 Supporting the system.........................................................................................................17
2.3.3 The siphon............................................................................................................................17
2.4 Sustainability...............................................................................................................................17
2.5 Manufacture ...............................................................................................................................18
2.6 Final Costs ...................................................................................................................................19
Thomas Pallister & Xaver Touschek......................................................................................................20
3 Storage...............................................................................................................................................21
3.1 Current storage methods in the Mekong Delta..........................................................................21
3.1.1 Flow chart of processes ...........................................................................................................21
3.2 Requirements for Storage system ..............................................................................................22
3.3 Ferrocement as a material..........................................................................................................24
3.3.1 Material composition matrix ...............................................................................................25

6. 5
3.4 Availability of materials for construction....................................................................................27
3.4.1 Portland cement ..................................................................................................................27
3.4.2 Fine grain sand.....................................................................................................................27
3.4.3 Potable water.......................................................................................................................27
3.4.4 Bamboo:...............................................................................................................................27
3.4.5 Wire mesh:...........................................................................................................................28
3.5 Ferrocement foundation theory.................................................................................................28
3.6 Water access...............................................................................................................................29
3.7 Concept design ........................................................................................................................31
3.8 Design development ..............................................................................................................31
3.8.1 Problem Identification .........................................................................................................31
3.8.2 Problem solutions ................................................................................................................32
3.9 Final design .................................................................................................................................34
3.10 Structural Analysis: ...................................................................................................................35
3.10.1 Analytical Conclusion:........................................................................................................35
3.11 Inlet filter ..................................................................................................................................35
3.12 Sustainable storage...................................................................................................................35
3.12.1 Life span of Tank ................................................................................................................35
3.12.2 Reducing ground Erosion...................................................................................................36
3.12.3 Flood Resistance ................................................................................................................36
3.12.4 Reduced Maintenance.......................................................................................................36
3.12.5 Locally Sourced Materials ..................................................................................................36
3.13 Storage Manufacture................................................................................................................36
3.14 Final Costing..............................................................................................................................37
3.15 Storage System Conclusion.......................................................................................................38
Callum Stephen & Nicholas Sidwell ......................................................................................................40
4 Filter Solutions ...............................................................................................................................41
4.1 User Requirement Specifications............................................................................................41
4.2 Potential Filtration Techniques.............................................................................................43
4.2.1 Slow Sand Filter....................................................................................................................43
4.2.2 Clay Pot ................................................................................................................................43
4.2.3 Why the Clay Pot?................................................................................................................44
4.2.4 How the clay pot Works.......................................................................................................44
4.2.5 Silver Nitrate Solution..........................................................................................................45
4.3 Filtration System Development ..................................................................................................46

7. 6
4.4 Clay Pot Filter development........................................................................................................47
4.4.3 Clay Pot Capacity..................................................................................................................47
4.4.4 Pot Lip ..................................................................................................................................49
4.4.5 Shrinkage during Firing ........................................................................................................49
4.5 Chemical Treatment of the water...............................................................................................50
4.5.1 Water Treatment Chemicals................................................................................................50
4.5.2 Silver Nitrate Solution..........................................................................................................50
4.6 Plastic Barrel Development.........................................................................................................51
4.6.1 Types of plastic.....................................................................................................................51
4.6.2 Initial Design.........................................................................................................................51
4.6.3 Changes in the design ..........................................................................................................52
4.6.4 The Lid..................................................................................................................................52
4.7 Detailed filtration design ............................................................................................................52
4.7.1 Key Dimensions....................................................................................................................53
4.7.2 Clay Pot ................................................................................................................................53
4.8 Manufacturing Filtration System ................................................................................................54
4.8.1 Manufacture of Clay Pot Prototype in the UK .....................................................................54
4.8.2 Clay Mix................................................................................................................................54
4.8.3 Clay Pot ................................................................................................................................54
4.8.4 Testing..................................................................................................................................54
4.8.5 Costs.....................................................................................................................................55
4.9 Manufacture in Vietnam.............................................................................................................56
4.9.1 Sourcing Clay Mix.................................................................................................................56
4.9.2 Clay Pot Moulding................................................................................................................57
4.9.3 Drying and Firing..................................................................................................................57
4.9.4 Reusing discarded Pots ........................................................................................................58
4.9.4 Treating with Silver Nitrate..................................................................................................59
4.9.5 Making the solution .............................................................................................................59
4.9.6 Applying the Silver Solution.................................................................................................60
4.9.7 Cost of Silver Solution..........................................................................................................60
4.10 Water Butt Manufacture ..........................................................................................................60
4.10.1 Plastic Barrel ......................................................................................................................60
4.10.2 Plastic Lid............................................................................................................................61
4.10.3 Plastic Tap ..........................................................................................................................61
4.11 Manufacture Costing ................................................................................................................62

8. 7
4.12 Filter Conclusion........................................................................................................................63
5 Discussion......................................................................................................................................64
5.1 Adaptability of the integrated system ........................................................................................64
5.2 Improvements on current methods............................................................................................64
5.3 Total cost of integrated system and funding:.............................................................................65
5.4 Worst Case Scenarios and Contingency Plans ............................................................................66
5.4.1Flooding ................................................................................................................................66
5.4.2 Typhoons..............................................................................................................................66
6 Conclusion..........................................................................................................................................67
7 References .........................................................................................................................................68
Appendix A - Material Calculations.......................................................................................................69
Appendix B – Construction Guidelines .................................................................................................70
Appendix C – Stress Analysis of Tank....................................................................................................76
Appendix D – CAD Drawings .................................................................................................................83
Appendix E – Bamboo Handling Techniques ........................................................................................84
Instructions for cutting .....................................................................................................................84
Instructions for splitting....................................................................................................................85
How to Split Bamboo? ......................................................................................................................85
Important: Bamboo has 2 sides! ..............................................................................................87
1. Straight Front:.........................................................................................................................87
2. Straight Cut Surface:.............................................................................................................88
Appendix F – Rainfall Data + Calculations.............................................................................................89
Appendix G – Example Meeting Minutes .............................................................................................90
Post holiday meeting (week 5) .........................................................................................................90
General points arising:..................................................................................................................90
Sectional updates:.........................................................................................................................90
Collection ......................................................................................................................................90
Storage..........................................................................................................................................90
Filtration........................................................................................................................................90
Other general points:....................................................................................................................90
Weekly meeting – week 12...............................................................................................................91
General points arising:..................................................................................................................91
Sectional updates:.........................................................................................................................91
Collection ......................................................................................................................................91
Storage..........................................................................................................................................91

9. 8
Filtration........................................................................................................................................91
Other general points:....................................................................................................................91
Figure 1 - Current guttering systems ....................................................................................................14
Figure 2 - Manual (left) vs. automatic (right) siphon............................................................................15
Figure 3 - Examples of automatic siphons ............................................................................................16
Figure 4 - Different methods to attach gutter to roof..........................................................................16
Figure 5 - Proposed method to attach gutter to roof...........................................................................17
Figure 6 - Supported guttering..............................................................................................................17
Figure 7 - Vietnamese People Splitting Bamboo ..................................................................................18
Figure 8 - Guttering on the Roof...........................................................................................................18
Figure 9 - Shaping Bamboo Supports to Hold Guttering ......................................................................18
Figure 10 - Storage process flowchart ..................................................................................................21
Figure 11 - Wire mesh...........................................................................................................................26
Figure 12 - Ferrocement foundation.....................................................................................................28
Figure 13 - Screw down tap ..................................................................................................................29
Figure 14 - Ball valve hose tap ..............................................................................................................29
Figure 15 - Loose head handle..............................................................................................................29
Figure 16 - Bent nose hose tap .............................................................................................................29
Figure 17 - Gate Valve tap.....................................................................................................................29
Figure 18- Design concept for ferrocement tank..................................................................................31
Figure 19 - Magnified view of tank displacements under load.............................................................33
Figure 20- Final tank design ..................................................................................................................34
Figure 21 - CAD drawing of inlet filter ..................................................................................................35
Figure 22 - Filtration Process Flow Chart..............................................................................................44
Figure 23 – Pore Size.............................................................................................................................45
Figure 24 - Filtration Processes.............................................................................................................45
Figure 25 - Filter Composition...............................................................................................................46
Figure 26 - Exploded View Of Filter System..........................................................................................46
Figure 27 - Clay Pot Internal Angle........................................................................................................47
Figure 28 - Final Filter Process ..............................................................................................................49
Figure 29 - Pot Lip .................................................................................................................................49
Figure 30 - Exploded View of Initial Design...........................................................................................51
Figure 31 - Detailed Filter Design..........................................................................................................52
Figure 32 -Key Dimensions of detailed design......................................................................................53
Figure 34 - Clay Pot Manufacturing Process.........................................................................................56
Figure 35 – Dry Bricks............................................................................................................................56
Figure 36 – Hammer Mill ......................................................................................................................57
Figure 37 - Press Mould ........................................................................................................................57
Figure 38 - Firing Process......................................................................................................................58
Figure 39 - Recycling Process................................................................................................................58
Figure 40 - Painting the Pot with Silver Solution ..................................................................................60
Figure 41: Blow Moulding.....................................................................................................................60
Figure 42 - Joining the Handle to the Lid ..............................................................................................61
Figure 43: Plastic Tap ............................................................................................................................61

10. 9
Figure 44 - Final cost breakdown..........................................................................................................65
Table 1 - Water source decision matrix................................................................................................14
Table 2 - Collection System Costing......................................................................................................19
Table 3 - Currently available storage options .......................................................................................21
Table 4 - Storage URS............................................................................................................................22
Table 5 - Decision matrix of different available storage methods........................................................23
Table 6 - Sang grading scale..................................................................................................................25
Table 7 - Material availability................................................................................................................28
Table 8 - Tap decision matrix................................................................................................................30
Table 9 - Tank construction process .....................................................................................................37
Table 10 - Final tank costings................................................................................................................38
Table 11 - Cost comparison...................................................................................................................39
Table 12 - Tank URS check ....................................................................................................................39
Table 13 - Filtration URS .......................................................................................................................42
Table 14 - Filter Decision Matrix...........................................................................................................43
Table 15 - Pros and Cons of a Larger Clay Pot.......................................................................................48
Table 16 – Types of Plastic....................................................................................................................51
Table 17 - Filter Costs............................................................................................................................55
Table 18 - Manufacture Costs...............................................................................................................62
Table 19 - Completed Filtration URS.....................................................................................................63
Team Assignment Overview
• Project Manager
• Storage designTom Pallister
• Collection design
• Introduction
• Team sketch artist
Kevin de
Michelis
• Collection design
• Worst Case Scenarios
• Project Management
Charles Heard
• Filtration design
Nicholas
Sidwell
• Filtration design
Callum
Stephen
• Storage
• Executive Summary
• Conclusion
• Construction Guide
Xaver Touschek

11. 10
1. Introduction
This report is a design solution for an Engineers Without Borders (EWB) Project in Vietnam.
1.1 Project Statement
Access to clean drinking water is an important issue that needs to be addressed throughout the
Mekong Delta region. Drinking water is currently collected from three sources: rainwater, boreholes
and surface water. Rainwater is collected in open cement /ceramic jars during the wet season and
will typically provide a family with water for approximately five months of the year. Impurity build
up in the jars is a problem. The approach should take account of the nature of the terrain and
culture of the region make good use of renewable sources of energy and the nature of the materials
available and include mechanism of decanting the water to and from storage.
1.2 Mekong Delta
The Mekong Delta is the region in the Anh Minh district in south-western Vietnam where the
Mekong River approaches and empties into the sea through a network of distributaries. Due to this
abundance of water and a six month monsoon season this is also an agricultural haven for the
Vietnamese rice farmers, and has numerous canals to aid the irrigation of the many rice fields. Thus
the area is referred to as flat flood plains and is, as implied, susceptible to floods during the wet
season. The wet season is a six month monsoon that South East Asia experiences in an annual rain
cycle, followed by a six month season of drought. The profusion of waterways means that the
principle mode of transport for both people and goods is boats and is otherwise very difficult to
access.
The average size for a rice farming family is 4.4 and they typically live in a house by the river or canal
to maximise the area of cultivatable land. The farmers are usually men as the work in the field is
considered ‘heavy’ work and for a man to do ‘light’ work, such as working in a factory, is culturally
unacceptable. However, though the women customarily do the ‘light’ work, they can work in the rice
fields too helping the men with several tasks, this is applicable to house building as well. Despite the
cultural gender separation in labour, men and women can work together to complete any necessary
task at hand; therefore any maintenance or construction can be performed by any member of the
family. The average wage of the rice farmers ranges from 6 - 9 USD/day.
1.3 Current Practice
As mentioned in the project statement drinking water is primarily collected from three sources
during the wet season. This water stored provides the family with enough to last them most of the
dry season. However, this means the farmers must compensate, for the deficiency of water, using
boreholes throughout the dry season, yet only 85% of the families have access to them. There is also
a lack of proper maintenance in there storage system; impurities build-up, in the open aired
jars/tanks, and requires too much time and effort to upkeep them leading to water contamination.
Moreover, there is no current practice with which to filter the water afterwards causing possible
infections and severe diseases due to bacterial accumulation and viral contagions.
Having assessed the major problems with the system currently in place, a preliminary set of criteria
was stated. Firstly, an improved system of storage had to be implemented, the new method had to
provide the family with sufficient water and minimise the risk of water contamination. Secondly,
filtered water adhering to international SPHERE standards had to be introduced to the families’ daily
lives to reduce the number of infection and disease outbreaks. For these two measures to be

12. 11
effective an efficient and clean water collection system also had to be added before the water
storage, to facilitate the rest of the operation. Finally, because of the very low salary of the people in
the region, the new system had to be financially viable and hence less expensive than the current
option.
1.4 Approach and Philosophy
There were two lines to follow when thinking of a solution to the problem at hand. There was a
communal approach and a domestic approach. The communal methodology was based around a
centralised water filtration plant, while a domestic attitude would have a system in and around the
homes of the agriculturalists. The communes, however, are not organised into villages with typical
clusters of housing or buildings. Although they are more densely populated in the centre, the houses
are spread out along the banks of the canals and waterways that criss-cross the district. It was
evident that having water filtration plants spread across the Anh Minh district would have been
cheaper to the individuals but that there was currently a lack of piping infrastructure; the
construction and maintenance of such a network would have been near impossible with the regular
floods. On the other hand a domestic approach encouraged better accessibility and higher flexibility
to the clean water, thus a domestic design was chosen.
The prerequisites to the design solution lead to an obvious attitude with which the project would be
handled. The knowledge and designs provided had to be accessible, understandable and executed
by the average farmer, allowing him to self-build his own clean water system. To implement this, the
design uses locally sourced materials and local businesses as well as providing clear instructions for
the construction. To make the process clear the solution was divided into three parts: the water
collection, the water storage and the water filtration. Each section can be addressed and dealt with
separately despite them complementing each other; this method facilitates the manipulation and
correction of any part. The final design provides a system that safely stores the water in a closed
environment before it is filtered and drunk. The ensuing report is thus separated into the following
three sections:

13. 12
1.5 Project Management
1.5.1 Planning
The project was split into the three sections early on, and each section was assigned two team
members;
 Collection – Charlie and Kevin
 Storage – Tom and Xaver
 Filtration – Callum and Nick
All the research and report writing for these sections were then to be done by their respective
members. Other areas were also assigned based on expected workload in the main sections;
 Introduction – Kevin
 Executive Summary – Xaver
 Worst Case Scenarios – Charlie
 Conclusion - Xaver
A Gantt chart was then made giving a schedule to the project (Appendix H).
Overall, the project followed the plan to a greater extent, some things took longer than expected –
the presentation for example put a complete stop to report writing for a week. The final order in
which the report was written and structured was changed adopt for this unexpected setback. An
initial finish date of three days before the deadline became just one; in which proof reading and final
editing took place.
1.5.2 URS and feasibility report
After the feasibility report, the group had a URS to work to and certain expectations of the project.
Unfortunately some of these quickly changed when detailed designs were drawn up. Costing, for
example, went up from $60 for the total system, to a total of just under $85. It was also discovered
that the guttering system should include a way to discard initial rainfalls; something not yet
discovered when the feasibility report was written.
The large initial URS was therefore edited slightly, removing some superfluous requirements, editing
others, and splitting it into sections for each part of the project.
1.5.3 Teamwork
The team met a minimum of twice a week throughout the project, these frequent meetings meant
that all members of the team were kept up to date with all other aspects of the project (Example of
minutes from some of these meetings can be found in Appendix G).
It also meant that most important decisions were made by the team as a whole rather than just the
team members assigned to that particular section. In a larger scale project this may have been
impractical but for this project it was a useful way to allow team members to support each other and
for no one team member to be overburdened at any point. The explanation of individual sections to
the whole team also worked as a way of reinforcing the understanding of one’s own and others’
sections as it highlighted things that were not fully understood or explained.

14. 13
Water collection
Charlie Heard & Kevin De Michelis

15. 14
Table 1 - Water source decision matrix
2. Collection
There are two main concerns to be addressed within the water collection: collecting and delivering
the water to the tank and removing any initial impurities that could contaminate the water before
storage. This comes in two statements in the URS;
 Collection of 4m3
in 2 months.
 Must allow water to be diverted away from tank to wash the roof.
The 4m3
was calculated for an average family of 4 requiring 3.8 litres/person/day for both drinking
and cooking.
2.1 Water sources
Currently in the Mekong Delta, there are three main sources of water used for both drinking and
cooking; canals, bore holes and rainwater. The three sources were analysed using the decision
matrix shown below and it was decided that, because “Falling rain can provide some of the cleanest
naturally occurring water that is available anywhere.”1
and can be collected with minimal effort, the
system should be designed around rainwater as a main source of water with contingency plans in
case this was not sufficient over the year. Calculations for rainfall data (table in Appendix F) between
years 2006 – 2010 shows that the wet season provides at least 83% of the year’s rainwater and that
a roof of 16m2
provides over 20m3
during this time. This quantity provides more than the required
needs.
Currently, those who use rainwater as a source of water
have some form of improvised guttering system, often
made from recycled materials and rubbish. While in
many cases this may be sufficient, customers will be
provided with a cheap effective alternative solution
either to replace the existing system if desired, or put in
place where a system is currently not present.
One key change to the guttering system will be the
addition of a siphon. After the dry season, it is likely that
dirt, bird droppings etc. will have built up over the roof
leaving it contaminated. This contamination should not
be allowed into the tank to help prevent bacteria build
up during storage. The simplest solution to this problem is to use the initial rainfall to wash the roof
and let the water flow elsewhere.
1
http://www.wateraid.org/uk/what_we_do/sustainable_technologies/technology_notes/246.asp
last access: 19/02/2013 12:16
Figure 1 - Current guttering systems

16. 15
2.2 Concept developments
Getting the water from the roof to the tank will be a different challenge for every home; the roofing
will be different in almost every case and the tank may not necessarily be built very close to the
house. It is therefore difficult to come up with a single standard system. Instead, as the whole
system is to be self-built, rough instruction guidelines will be provided to the user on how to build a
system based on general guidelines and construction techniques.
The main construction material chosen was bamboo; it is the most readily available material, very
inexpensive and environmentally friendly. It will be used both as structural support and, when split,
the gutter itself.
As for the initial filter, this will be the same design for every customer. The first two rainfalls2
at the
start of the rainy season will be drained away to ensure none of the dirt accumulated on the roof
over the dry season pollutes the tank water. While the water is destined for a filter, it is beneficial to
store the water as cleanly as possible to prevent obstructing the tap or breeding bacteria. So to
implement this effectively a system had to be designed to allow for water to be diverted away from
the tank and then easily redirected.
There are essentially two ways to approach this, an automated system, whereby the system will
automatically siphon off the initial water and then divert the rest into the tank, or a more basic
system whereby the user will have to divert the water themselves.
Figure 2 - Manual (left) vs. automatic (right) siphon
The manual siphon, shown in Figure 2 demonstrates the basic concept of ‘completing the circuit’. By
having a removable piece the customer decides when to allow the water to flow into the tank, thus a
reference must be accompanied with the siphon to indicate the appropriate amount of water to
discard before ‘completing the circuit’.
As for the automatic system, there are several simple mechanical systems that could be considered,
most utilising something buoyant to close up a valve or fill a hole once 20 litres have been stored in a
container. Then the only maintenance is to empty it once a year before the rainy season starts
2
www.unicef.org/eapro/Harvesting_the_rain_p_29-42.pdf (last viewed 4/3/13 15:47)

17. 16
Figure 3 - Examples of automatic siphons
In figure 3, two examples are given of simple systems;
On the left is an example using two buoyant balls. As the container fills with water, the ball inside
floats to the top of the container and pulls, via the rope, the left hand ball into the hole, filling it and
diverting the rest of the water straight down the gutter.
On the right is a simple float in a tank, which floats to the top, filling the hole and diverting the water.
Both are very simple to implement and contain only a few moving parts which are unlikely to fail or
require much maintenance.
While an automatic system removes the chances of human error (the manual system requires the
user to remember to remove and replace the section of gutter) and is much more user friendly,
there are some downsides. The mechanical system is more complicated, both to make and maintain
and requires additional materials to construct. Moreover, the weight of the collected water has to
be supported in addition to the gutter.
2.3 Final design
The three final detailed aspects of the design are attaching the gutter to the roof, supporting the
system and the manual siphon.
2.3.1 Attaching to the roof
Figure 4 - Different methods to attach gutter to roof
3
Several methods were examined as shown in figure 4. To best suit the available materials however, a
slightly altered method has been adopted. Using smaller diameter bamboo poles, two runners will
be made to hold the gutter. These can then be lashed to the struts in the roof with rope.
3
http://www.unicef.org/eapro/Harvesting_the_rain_p_29-42.pdf (last viewed 4/3/13 19:17)

18. 17
Figure 6 - Supported guttering
Figure 5 - Proposed method to attach gutter to roof
Figure 5 illustrates this system put into place. This solution is simple and in-keeping with the current
construction of the roof and allows for guttering to be attached to multiple sides of the roof to
collect the desired amount of water.
2.3.2 Supporting the system
In appendix E is a set of instructions provided by guaduabamboo on
using bamboo as a construction material. Using these methods the
user will be required to erect some supporting poles to take the
weight of the gutter full of water.
These poles should be dug into the ground, approximately 30cm to
ensure they don’t fall over, and need to be provided every 1m along
any guttering between the roof and the tank.
2.3.3 The siphon
It was decided that a manual siphon was a more feasible solution due to the increased construction
and weight of the automatic system. The system is very easy to implement. In the section of
guttering between the roof and the tank a piece of gutter shall be made to be removable.
This system fully completes the desired requirements set out in the URS – it is capable of collecting
4m3
and has a siphon to remove water.
2.4 Sustainability
Bamboo is the most readily available material to the Mekong Delta. It is grown in communal farms
for various purposes, mainly construction. The local inhabitants can easily access the bamboo grown
on these farms, however, the high demand of this material makes these communes very difficult to
maintain. Therefore the sustainability of these bamboo farms must be taken into consideration to
ensure that the material is still readily available to other people in the Mekong Delta. If necessary, it
is possible to purchase the bamboo that has been cut and pre-treated for construction purposes.
The bamboo can be delivered to the Mekong Delta however, the cost must inevitably be considered
if this choice were to be acted upon.
If you put the bamboo into the ground, it will last up to 2 years, then it will rot off at the ground level.
Above the ground the bamboo will last many, many years. If outdoors in the elements it will likely
last more than 10 years. It is naturally rot and pest resistant.4
4
Reference: www.bamboosupply.net/faq.htm

19. 18
Figure 7 - Vietnamese People Splitting Bamboo
Figure 8 - Guttering on the Roof
2.5 Manufacture
This design for manufacture will be made for a standard sized roof of 4m x 4m. The design standard
is simply to facilitate a manufacturing guide as all the roof sizes, and hence material requirements,
will be different. Though it cannot be assumed that the user knows the process of making guttering,
it is well known that the farmers have their own self-built guttering system. Therefore, the following
is a rough guide and not a set of strict instructions. It is even possible that there is no need to supply
them with the guide as they may very well have their own system in place; therefore these
guidelines may not be applicable to all users but are of a higher importance if a new house is to be
built.
A 4m x 4m roof will have gutters running along three sides of it, two on the ends of the slants and
one connecting them. A fourth piece of guttering, again adjustable to user requirements, will join
the set of gutters to the tank; this piece will be taken to be 4m long as well. The fourth gutter will be
tied and supported further along. The support will also be made of bamboo as it is sufficient for the
job at hand.
A total of 20m, of a 10cm diameter bamboo species,
for the gutters and supports will be used. The roof
support bamboo should use small, sturdy poles,
typically with diameter of 2cm; a total of 19.2m will be
used. For the construction of the gutters two of the
large poles will be cut into 4m lengths and split in half
(using the techniques given in the Appendix E), then,
the nodes are removed with a knife or chisel, to make
a gutter shape. There should now be four 4m gutters
ready for installation.
The two gutters on the roof that capture the runoff
water will be attached to the roof using natural fibre
ropes and the small bamboo poles. There are two 4m
runners per side and then two 30cm strips per metre per
side, thus eight support junctions in total. Each of the
support junctions will use 2m of fibre rope. The third roof
gutter will be placed on the side of the house closest to
the tank. One end will be attached to one gutter while
the other end will rest on the fourth tank-gutter, as
shown in figure 8.
Supports will be placed with two meter
spacing along the fourth gutter: one at the
connection point with the roof gutters, and
one halfway along. The final support will be
the tank. To make the supports a shape that
will better accommodate the resting gutters,
Figure 9 - Shaping Bamboo Supports to Hold Guttering

20. 19
the end must be cut in a ‘U’ shape as shown in figure 9. The supports should be buried at least 30cm
into the ground to ensure adequate stability. Four metres of bamboo has been estimated for the
supports though the height of the bamboo poles needed depends wholly on the height of the user’s
house.
The fourth gutter can now be cut in half; leaving one end permanently fixed at the roof connection
and the other half now a removable piece as discussed in the concept development.
2.6 Final Costs
Using the lengths and quantities stated in the manufacturing for design, the costs calculated are
given in table 2.
Table 2 - Collection System Costing
Material Cost per unit Quantity Cost
10cm Bamboo $0.1/m 4 x 5 =20 metres $2.00
2cm Bamboo $0.1/m (4 x 4) + (2 x 8 x 0.3) =
20.8 metres
$2.08
Fibre Rope $0.3/m 2 x 8 = 16 metres $4.80
Total Cost: $8.88

21. 20
Water Storage
Thomas Pallister & Xaver Touschek

22. 21
3 Storage
3.1 Current storage methods in the Mekong Delta
Rainwater harvesting is common throughout the Mekong Delta region. The current storage method
adopted by many households is to have large ceramic, open-top jars placed adjacent to the
household. This is normally accompanied by an improvised guttering system that channels rainwater
from the roof to the jar itself. However, there are many disadvantages with this method. Firstly the
storage capacity of these jars is limited to a maximum of 1000 litres which is an insufficient volume
to adequately provide for a family of 4 during the 6 month dry season. Secondly, the fact that these
jars are open-top means that there are serious implications for the quality of water stored inside.
When stored water is exposed to sunlight and air, bacteria can grow as well as other water borne
viruses such as e-coli. This exposure also allows the water to be contaminated with impurities such
as debris or insects. Lastly, these jars are prone to breaking and frequently need to be replaced
which places a financial strain on the families.
There are other storage options available in the Mekong Delta such as plastic water tanks.
However, these options are frequently more expensive than the ceramic jars. Table 3 shows the
projected cost of installing a sufficient number of water tanks that will provide for a family of 4
during a 6 month dry season:
Table 3 - Currently available storage options
Storage option Capacity Individual Cost Total Cost
Ceramic Jars 1000 litres $20 $80
Plastic Water Tanks 1000 litres
500 litres
$80
$50
$320
$400
As illustrated, it is far less expensive to install a system of ceramic jars rather than plastic tanks.
However, installing ceramic jars incurs all the disadvantages mentioned previously.
3.1.1 Flow chart of processes
Figure 10 illustrates the processes that have to be considered when approaching a final design of the
storage system.
Figure 10 - Storage process flowchart
Water
entrance
•How the water will enter
the storage system from
the guttering.
Storage
•Manner in which the
water is stored in the
system.
Water
access
•How the user
can easily
access the
water when
required

23. 22
3.2 Requirements for Storage system
The design concept for the water tank will be based upon the following requirement specifications.
Should any aspect of the tank design not fulfil the requirements table below then it will not be
considered for further development.
Table 4 - Storage URS
Category Requirements
Functional
Requirements
Must store 3,600 litres of water (900 litres per person).
Technical Requirements
Must not allow direct exposure to sunlight.
Materials used be available locally in the Mekong Delta.
Tank must be available to build for under $80.
Implementation and on-site construction time must be under 2
weeks to allow for immediate use.
Can be built by an unskilled labourer.
Must safely withstand the internal pressures of the tank at full
capacity.
Operational
Requirements
Water access must have a minimum flow rate of 7.5
litres/minute.
Tank can be easily maintained by an unskilled labourer.
The main problem to solve with the water storage solution is the sheer amount of water that needs
to be stored. To see the average family of 4 through a 6 month dry season, 3600L (900L per person)
is needed for cooking and drinking. Another main factor to consider is the cost of the tank. It must
be affordable on the average wage of a Mekong Delta rice picker to ensure the tank can be
purchased by the people who need it most. The target cost was less than $80 as this is the price to
store the same amount of water using the current ceramic jars. This would make the tank an
extremely attractive option as it would be cheaper and more hygienic. The last major challenge to
face is creating a tank that is hygienic. To do this the tank must be kept out of direct sunlight and
allow minimal exposure to air. This is a significant challenge as the tank must have entry and exit
points for the water.
Research was then conducted into the various methods of rainwater storage currently used around
the world. The methods investigated and the decision matrix are shown on the following page.

24. 23
Thismatrixisbasedonacolourcategoryandquantifiedsystem.Thekeyforeachcolourisshown(bottomright)andavalueforeachcolourisgiven.The
specificationsaredividedinto‘Musts’and‘Wants’.Eachspecificationhasanumericalvaluerelatingtoitsimportancewhichisthenmultipliedbythe
valueofthecolour,theproductofwhichisshowninthebox.The‘Feasible’sectionisthesumofeachstoragemethod.Themethodswiththehighest
valueswillbetheonesthatshouldbefurtherconsidered
Thereareseveraldifferentmethodsofwaterstorageavailabletothedevelopedworld.However,asthedecisionmatrixshows,manyofthesedonotmeetthe
URS.
Table 5 - Decision matrix of different available storage methods

25. 24
3.3 Ferrocement as a material
Ferrocement is a form of reinforced concrete that differs from the conventional reinforced or pre-
stressed concrete that is commonly used in industrial building. The principle difference between the
two is the manner in which the reinforcing elements are arranged and dispersed within the mortar.
The reinforcement for ferrocement normally consists of closely spaced layers of wire mesh that are
supported by rods or poles; cement mortar is then applied over the mesh. The resultant composite
material formed has different behavioural characteristics in terms of strength, deformation and
potential applications.
Although the name implies a ferrous reinforcement, the same characteristics can still be achieved
using materials other than steel meshes or rod. This ensures that the use of ferrocement is not
subjected purely to countries or communities that have quick and inexpensive access to ferrous
materials. Indeed, replacement materials for steel meshes that have been used, either in practice or
purely for experimentation, have included organic woven fabrics such as polypropylene and organic
natural fabrics made with jute, burlap, or bamboo fibres.
Ferrocement also has a very high tensile strength-to-weight ratio and a superior cracking behaviour
in comparison to conventional reinforced concrete. This means that structures made out of
ferrocement can be made relatively light and water tight. Furthermore the malleability of the
reinforcement meshes allows one to easily alter the dimensions of a structure. These characteristics
make ferrocement an attractive material for water tight structures such as water tanks and barges.
The basic construction process for any ferrocement structure is as follows:
1. Initial foundation that is appropriate to the structure being built.
2. Construction of steel rods (or other material) to form a skeletal framing.
3. Attaching mesh to skeletal framing.
4. Plastering of mortar.
5. Curing.
The simplistic construction processes means that only low level technical skills are required and the
fabrication of small scale projects can be performed by an unskilled labourer.
The following conclusions are based on a report on ferrocement water tanks, conducted by the
Science Museum of Virginia:5
1. Ferrocement is an economically feasible material for the construction of water storage tanks.
2. Flexibility of shape, freedom from corrosion, possibility of hot storage, relative lack of
maintenance, and ductile mode of failure are important advantages of ferrocement over
other materials commonly used for low to medium pressure (up to 345kPa) storage of fluids.
3. Ferrocement tanks require less energy to produce than steel tanks.
Therefore ferrocement, as a material, appears to have the largest potential to fulfil the user
requirements specifications.
5
http://www.bpesol.com/bachphuong/media/images/book/549r_97.pdf (last accessed 5/3/2013 15:31)

26. 25
3.3.1 Material composition matrix
Ferrocement consists of Portland mortar, reinforcement, admixtures and coatings. To achieve the
appropriate tensile and compressive strength characteristics of the tank it is necessary to perfect the
proportions of the mortar components. This is dependent upon the nature of the sand, chemical
composition of the cement, the water-cement ratio and the curing of the finished tank.
3.3.1.1 Matrix mix proportions
The mix proportions’ ranges for ferrocement mortar are as follows6
:
• Sand - Cement ration by weight: 1.4 - 2.5 : 1
• Water - Cement ratio by weight: 0.3 - 0.5 : 1
These ranges have yielded satisfactory results and should be adhered to when constructing the tank.
The quality of sand factors greatly towards a high calibre mortar. Well graded, rounded, natural sand
having a maximum top size of about one-third of the smallest opening in the reinforcing system to
ensure proper penetration. 7
The water used should also be of relatively high quality and free from
contaminated organic matter. The presence of these impurities will weaken the mortar matrix.
Curing the ferrocement once construction has finished is important for attaining the maximum
strength characteristics of the mortar and the prevention of cracking. Curing can be performed by
either wetting the surfaces regularly or covering the structure in polythene sheeting to contain the
moisture. This process must be maintained for at least two weeks before the structure is suitable for
use.
3.3.1.2 Sand
The desirable sand grading for ferrocement mortar is as follows:8
Table 6 - Sang grading scale
Sieve Per cent Passing
3/8 in. (9.5 mm) 100
No. 4 (4.75mm) 95 – 100
No. 8 (2.36mm) 80 – 100
No. 14 (1.18mm) 50 – 85
No. 30 (600μm) 25 – 60
No. 100 (150μm) 2 – 10
3.3.2 Reinforcement
The reinforcement of ferrocement is commonly in the form of intertwined wire that creates a mesh.
Traditionally the mesh layers are attached by hand to a framework of poles and the mortar is applied
to the meshed structure and plastered on either side. The wire mesh acts to distribute the loads
experienced within the tank through the mortar and across the structural frame. However, this
method is liable to create voids on the peripheries of the rods. In fact, U.S. Navy research on high-
performance ferrocement hulls concluded that steel rods were ineffective at reinforcing a structure
6
ACI Committee 549, ‘State-of-the-art Report on Ferrocement’, January 24 1997, p 7.
7
Ibid p. 7.
8
United Nations High Commissioner for Refugees, ‘Large Ferro-Cement Water Tank, Design Parameters and
Construction Details’, July 2006, p. 16.

27. 26
and in some cases are detrimental to the structural stability of the final product9
. This is because the
poles are not loaded to take advantage of their strength; the spacing they create when the mortar is
applied allows for regions of unreinforced mortar that contributes to weight but not to strength.
They actually act as stress concentrators. The need for steel rods was eliminated by applying the
mortar to the mesh which is supported by frames made of wood strips, ply wood and even bamboo.
Therefore the requirements for the reinforcement of the ferrocement tank can easily be
accomplished using bamboo for the structural framework and chicken wire as the mesh. Not only
can the same strength characteristics be achieved using these materials but it also eliminates the
need for steel to be used for the framework which saves money on material expenses.
3.3.2.1 Wire Mesh
According to the United Nations High Commission for Refugees,
the ideal type of wire mesh for use in ferrocement structures
should have the following properties.10
1. Must be easy to handle and flexible enough to bend.
2. Galvanized wire mesh is preferable as it is less likely to rust or
corrode.
3. 0.5 - 1.0 mm diameter with 10 - 25 mm mesh opening.
4. Free from grease and anything that might reduce bond.
3.3.2.2 Bamboo
Despite the convenience of using bamboo for the framework, it still needs to well treated before
construction. Untreated bamboo poles have the distinct risk of swelling when in contact with
ferrocement that is settling. Therefore preparation must be taken with the sizing, seasoning and
waterproofing.
Split bamboo is generally more desirable than whole culms as reinforcement. Hollowed
bamboo creates stress concentration points within the ferrocement which can affect the structural
stability of the tank. By splitting the culm in half these stress concentration points are avoided.
Splitting the bamboo can be done by separating the base with a sharp knife then, using a dull blade,
continue this separation throughout the culm.
When possible, the bamboo should be cut and allowed to dry and season at least 3 – 4
weeks prior to construction 11
. Seasoning the bamboo allows it to increase its strength
characteristics. During this process the culms should be supported at regular intervals to avoid
warping.
When seasoned bamboo, either split or whole, is used as reinforcement, it should receive a
waterproof coating to reduce swelling when in contact with concrete. Without any coating the
bamboo will swell before the ferrocement has settled and developed sufficient strength to prevent
cracking. However, only a thin layer should be applied; thick layers tend to lubricate the surface of
the bamboo and consequently the bonds with the ferrocement mortar will weaken. The type of
coating will inevitably depend on the materials available in the Mekong Delta.
9
ACI Committee 549, ‘State-of-the-art Report on Ferrocement’, January 24 1997, p 7.
10
United Nations High Commissioner for Refugees, ‘Large Ferro-Cement Water Tank, Design Parameters and
Construction Details’, July 2006, p. 16.
11
Francis E. Brink and Paul J. Rush ‘BAMBOO REINFORCED CONCRETE CONSTRUCTION’, Port Hueneme,
California, February 1966, p.4.
10 -25 mm
Figure 11 - Wire mesh

28. 27
3.4 Availability of materials for construction
When building any structure using ferrocement it is highly important that the ingredients are readily
and locally available. In the research it was ensured that there were two reliable sources of
materials; an ideal first option and a contingency option if the 1st
proves to be unfeasible. The
principle materials required for the construction of a ferrocement structure are listed as follows:
• Portland cement.
• Fine-grain sand.
• Potable and organic matter-free water.
• Wire mesh.
• Bamboo poles for frame work.
3.4.1 Portland cement
The most readily available cement to the Mekong Delta is Portland cement PCB40 which has various
advantageous characteristics. Its low alkali content helps improve the concrete’s durability and
prevents steel inside the concrete from being corroded by alkali-aggregate reactions, PCB40 meets
the American standards for cement12
. This cement is manufactured by a Vietnamese based company
called Thang Long Cement who supplies their products to the Mekong Delta Region. However, if for
some unexplained reason this option is unfeasible then there is a cement factory located in Rach Gia
which is in the Mekong Delta region13
. Portland cement can very easily be sourced from this factory.
3.4.2 Fine grain sand
According to the research this is readily available to the communes of the Mekong Delta. In fact the
sand on the banks of the Mekong Delta is used as a source of mortar sand for the whole of Vietnam.
Its quality and abundance fortunately means that there is a plentiful supply of mortar sand available
to people in the Mekong Delta.
3.4.3 Potable water
The water quality of borehole water and harvested rainwater is sufficient enough to yield a good
quality mortar but not water from the river. Borehole wells are accessible to 85%14
of households in
the Mekong Delta whilst all other households already have in place methods of storing large
quantities of rainwater. Rainwater is the preferable option for mixing the mortar as it is of a better
quality than borehole water. However, stored rainwater is obviously a precious commodity so any
opportunity to conserve it must be acted upon. If the use of rainwater proves to be far too
impractical and detrimental to a household then borehole water is of a satisfactory quality for
mortar mixing.
3.4.4 Bamboo:
As stated in section 2.4, bamboo is a highly adequate material and ideal for the construction of the
tank.
12
http://thanglongcement.com.vn/en/news/company-news/thang-long-cement-jsc-is-listed-in-the-
prestigious-vnr500-ranking-board. Last accessed 03/03/2013.
13
http://www.ewb.org.au/discussions/1273/11437’ last accessed 05/03/2013.
14
http://www.ewb.org.au/explore/initiatives/ewbchallenge/hfhewbchallenge/hfhwash last accessed
01/03/2013

29. 28
Rebar frame
Figure 12 - Ferrocement foundation
3.4.5 Wire mesh:
Wire mesh is a very common material available to everyone in the Mekong Delta at a set price. Sold
at a set width of 1.6 metres it is an essential material for farming and fishing techniques of all
families.15
The table below summarises the ideal and contingency material availability in the Mekong Delta.
Table 7 - Material availability
3.5 Ferrocement foundation theory
The construction of a secure and level foundation is crucial for the structural stability of any building.
The process can often be very time-consuming as well as requiring a large work force. Fortunately, in
the case of small scale ferrocement water tanks, the construction process for a suitable foundation is
not complicated and does not require many labour hours.
As with all building processes, the initial step is to clear all debris and level the site upon which the
storage system will be constructed. After this the topsoil is removed to an appropriate depth. In
cases where structures exert large stresses upon the soil beneath the foundation it is usually
compressed to help it attain maximum strength. This is also necessary for a domestic water storage
system but since the hydrostatic stresses are well below those exerted by large buildings the
compaction does not need to be
extensive. The next stage is to lay the
rebar frames which are normally steel
bars; however, this material may be an
expensive commodity locally. It is
possible, though, to replace the steel
bars with bamboo poles. The rebar
frames provide reinforcement for the
ferrocement mortar that is then
poured on top. There is the option of
placing a layer of gravel beneath the rebar frames, however, this is not essential for small scale
water tanks. The frame work for the tank then needs to be attached to the rebar frames and
embedded into the ground. The frame work provides the skeletal shape of the final tank. After the
frame work poles are inserted comes the final stage of pouring the cement mortar over the rebar
frame. The concrete pad should be left to settle and once dry, building the tank can commence.
15
http://www.ewb.org.au/discussions/1273/11407’ last accessed 07/03/2013
Material 1st
Option Contingency
Cement Thang Long cement (PCB40). Local factory in Rach Gia.
Sand Sourced from Mekong River banks. Purchased locally.
Bamboo Bamboo poles from communal farms. Purchase pre-treated bamboo locally.
Water Rainwater from harvested sources. Borehole water.
Wire mesh Readily available at local hardware stores

30. 29
3.6 Water access
The selection of an appropriate, effective tap is an important decision for ease of user interface. A
valve or tap is the only means for the consumer to gain access to the harvested water. A tap
attached to a tank is often gravity fed by the pressure of the water from the tank. It is also safe to
assume that the tap will be in constant daily use. Therefore it is necessary to choose a tap that can
deal with both heavy usage and large pressures without failing or, more importantly, wasting water.
Consideration must also be given as to the ease of pouring the water into a bucket without risk of
waste. To finalise a solution, it is necessary to research the positives and negatives of the different
types of water valves and taps available.
Screw down tap
These taps use a screw valve mechanism and are the most popular type of outdoor tap used by
homeowners. The handle or wheel of the tap is turned by the user and this causes the internal stem
to move up or down, thereby controlling the exit flow of water. However, because of the screw valve
design, these taps tend to wear out frequently and can be difficult to turn after long periods of
disuse.
Figure 13 - Screw down tap Figure 14 - Ball valve hose tap Figure 15 - Loose head handle
Figure 17 - Gate Valve tapFigure 16 - Bent nose hose tap

31. 30
Decision Analysis
Tap types
M
ustcope
w
ith
large
pressures
Ease
ofuserinterface
W
ide
range
ofadjustable
w
aterflow
Length
oftim
e
offunctionality
Ease
ofm
aintenance
/replacem
ent
Screw
threads
to
allow
attachm
ents
Safety
againstunauthorised
w
atercollection
Presense
ofnozzle
foreasiercollection
Feasible
Screw down tap 5 5 5 3 3 1 1 5 28 5 Suitable
Ball-valve hose tap 5 5 3 5 5 1 1 5 30 3 Not quite suitable
Loose-key handle tap 5 5 5 3 3 1 5 5 32 1 Unsuitable
Bent-nose taps 5 3 3 3 3 5 1 1 24 0 Completely Unsuitable
Gate valves 5 3 3 5 3 5 1 1 26
Ball-valve hose tap
Ball valve hose taps use a rotational-motion handle (usually a 90° lever or quarter turn wheel) to
access water quickly and easily. The ball-valve style is a simple yet effective mechanism that is
durable, long-lasting and easy to use. These taps are also available with a nozzle to allow for the
water to be ejected horizontally. However, the tap doesn’t allow for mid-range water flow
adjustment.
Loose-Key Handle taps
These taps function in the same manner as screw down taps however, the handles can be removed
when not in use to control the water. This helps reduce water wastage and prevents unauthorised
water usage. However, the same problems are encountered as the screw down tap.
Bent-Nose Hose Taps
Bent-nose hose taps are screw-style valves attached to vertical pipes that have outlets slanted down
at a 45-degree angle to avoid hose crimping. These taps are generally placed in garden and lawn
areas as a stand-alone water source for hose or sprinkler hook-ups.
Gate valves
Gate valves are controlled by a wheel-style handle. The mechanism allows for adjustable flow
control and requires little maintenance. The valves function well for both high and low pressure
systems and is relatively inexpensive. However, the lack of a nozzle will result in difficulties in
collecting the water and the valve is not very forgiving of grit in water.
Decision Matrix
Conclusion:
From the decision matrix it is clear that the loose-key handle tap best satisfies the user requirements.
The tap has the best combination of both ease of user interface and safety against unauthorised
water collection. However, despite the positive aspects of this tap there is the distinct danger that
the detachable handle can either be lost or stolen, rendering access to the harvested water
impossible.
Table 8 - Tap decision matrix

32. 31
3.7 Concept design
Once ferrocement had been confirmed as a viable building
material the procedure of implementing it in a water tank
design was undertaken. Figure 18 shows the concept design
of the tank. The tap was located 10cm above the base of the
tank to allow access to 93.3% of the 4m3
. The remaining
water left at the bottom of the tank is used to allow a degree
of debris to be deposited before the water extracted contains
any debris. A wash out pipe of 2.5cm is located at ground
level so if contamination is identified it is possible to evacuate
the tank to clean it. This washout pipe is blocked by a bung.
The initial did not include a roof thus allowing access to the
tank. This also allowed the tank to collect water that lands on
the area. Although this does allow exposure to direct sunlight,
which aids bacteria growth, as filtration occurs after storage;
the problem was considered less important than access to the
tank.
The tank dimensions are 1.5m in height with a diameter of 1.85m. The foundations extend 10cm into
the ground to ensure a secure structure. 20 bamboo poles are used in the outer wall as supports for
the wire mesh to be wrapped around. This means a support every 30cm around the perimeter;
ensuring a pure curve is retained when the wire mesh is wrapped round. A pure curve ensures that
the tank does not experience stress concentrations in corners unlike a square structure. The wall
thickness used is 3cm, as research on current ferrocement tanks used in Western African countries16
revealed this thickness is sufficient, and their African counterparts experience a higher hydrostatic
pressure. The maximum hydrostatic pressure experienced in the concept tank is 15kPa giving the
concept tank a factor of safety of 10. The advantage of a higher pressure is an increased flow rate of
water; however, a more robust wall is required to withstand a higher pressure.
3.8 Design development
3.8.1 Problem Identification
The initial concept achieved some of the URS, however, failed in other key areas; mainly as it
allowed exposure to direct sunlight. Another potential failure was that, although when properly
constructed the tank easily withstood the hydrostatic pressure, the tank was to be constructed by an
unskilled labourer. This may result in thin areas that could result in cracks. Exposure to air is another
problem; that can result in bacteria growth acceleration or mosquito infection and ideally would be
eliminated or minimised.
The tank has a volume of 4m3
due to its height and diameter, but 0.27m3
of this is inaccessible as it
is stored below than the level of the tap and 0.13m3
is not able to store water as it is above the level
of the overflow pipe. This leaves 3.6m3
of accessible water. This meets our requirement, however,
does not allow for a margin of error for the mistakes of an unskilled worker, or for a head of water to
create pressure for the tap. Using hollow bamboo poles was also identified as a possible weakness in
16 http://www.akvo.org/blog/?p=997 last accessed 2/3/13
Figure 18- Design concept for ferrocement tank

33. 32
the design, as with a diameter of 2cm, the poles would only have 0.5cm wall thickness. This
significantly reduces the strength of the tank around the pole areas.
3.8.2 Problem solutions
3.8.2.1 Addition of a Roof
As a result of these problems modifications were made to the tank design. A roof and inlet filter
were added as this eliminated exposure to sunlight achieving another URS target. The roof slants at
a shallow angle into the centre of the tank, meaning water that lands on the tank can flow into it.
This also allowed the tank to be filled with borehole water in the event of a severe drought or similar
event. However, as a slope was required this meant that 10cm at the top of the tank volume was
lost. The inlet filter is constructed of two layers; one wire mesh layer followed by a cloth layer. The
wire mesh first filters out any large debris like leaves and twigs whereas the cloth filters out smaller
particles like sand and silt in borehole water. The cloth layer also stops mosquitos accessing the tank
to breed. To stop mosquitos accessing the tank the overflow pipe was also covered with a cloth layer.
3.8.2.2 Increasing the Diameter of the Washout Pipe
Adding the lid did remove the ability to access the tank insides, however, as it hugely reduced the
chance of contamination and reduced the amount of maintenance. The largest particle that can fit
through the wire mesh is 2.5cm. Due to this, the washout valve diameter was increased from 2.5cm
to 5cm allowing the maximum sized particle to be expelled from the tank easily. To support the roof
two internal walls were added extending from opposite sides of the tank towards each other, leaving
a 10cm gap between them, allowing water flow throughout the tank. This internal wall also
increased the factor of safety of the tank.
3.8.2.3 Increasing Tank Capacity
The diameter of the tank was increased from 1.85m to 1.95m in order to store more water. This left
a margin of error for an unskilled worker. It also equated for the loss of water due to the slope of the
roof. The increase in volume left a volume of 0.28m3
as a margin of error for the unskilled worker
and water pressure.
3.8.2.4 Addition of Basion
To make the tank a more sustainable structure a basin was added to the water access point. This
reduces erosion around the tap area that could potentially compromise the integrity of the
foundations. The basin is dug into the ground which allows easy water access. Without the lowered
basin; there is only a 10cm space to fit a water carrying vessel under the tap. Conversely, with the
basin, this is increased to a 25cm space. This also provides a deeper foundation point as it goes 30cm
into the ground increasing flood resistance
3.8.2.5 Increasing Wall Thickness
Another problem to overcome was the wall dimensions; which could be inconsistent. The wall
thickness was increased to 5cm instead of 3cm to account for this. As a result; there is a large margin
of error in construction in case of wall thickness inconsistency or an incorrect cement ratios.
Hopefully these problems will be minimised by the construction guide shown in Appendix B. This
adjustment resulted in a minimum factor of safety of 36 increasing to a maximum of 39000, as
shown in the structural analysis in Appendix C. This is far in excess of the 10 required for tanks, and
means that the tank is extremely resistant to impacts such as debris in flooding.

34. 33
3.8.2.6 Splitting Bamboo
To solve the problem of using hollow
bamboo poles it was decided to use split
poles for the tank construction. This helps
improve the strength of the tank as there
are no longer cavities in the structure.
Splitting the poles also prolongs the life of
the tank by reducing the bamboos exposure
to air which carries microbes capable of
reducing the strength of the bamboo.
Figure 19 - Magnified view of tank displacements under load

35. 34
3.9 Final design
Washout valve to allow evacuation
if the tank becomes contaminated
(located behind tank)
Overflow valve to stop tank
overflowing, slew gate system
to stop exposure to the air
(located behind tank)
Inlet filter to stop dirt and
debris entering the tank also
reducing exposure to air and
sunlight
5cm thick walls to help withstand
impacts in flood situations
Loose key tap to allow
restricted water
access
10cm foundation to provide a solid
base for flood resistance
Water basin to stop
ground erosion and
reduce water
spillage
Roof slanted to capture
water landing on the area
Internal walls used to support roof
structure and strengthen tank
Cylinder chosen
to reduce stress
concentration in
corners
Tap located 10cm above
foundation to access the majority
of water in the tank and allows any
debris to sink; not contaminating
the access point.
Figure 20- Final tank design
For dimensions please see CAD drawings in Appendix D

36. 35
3.10 Structural Analysis:
The stress analysis of the ferrocement water tank is of critical importance to the success of the
project. If the design fails to cope with the considerable internal hydrostatic pressure then it would
be entirely unfeasible to construct the tank.
The model program used for analysis is SolidWorks Simulation and this report summarizes the
stress analysis results of the water tank simulation. The stress analysis report can be found in
Appendix C.
3.10.1 Analytical Conclusion:
From the stress analysis report, the factor of safety for the tank under the Max von Mises stress
ranges from a minimum of 30 to a maximum of 39000. These values were calculated using a
uniformly distributed pressure within the tank of 15 kPa; the maximum hydrostatic pressure
experienced at the bottom of the tank at full capacity. The safety factor range is far in excess of
what is required to create a water tank, however, as the tank is constructed by an unskilled
worker, this margin of error is required to make up for any mistakes of procedural errors in the
manufacturing process. It is therefore safe to assume that the structure of the tank will not fail
under full capacity and can therefore be constructed.
3.11 Inlet filter
In the URS, one of the requirements was to avoid exposure to sunlight and fresh air. To achieve this,
yet still have the ability for water to pour in through the top of the tank, a special inlet filter has
been designed.
This simple, small, removable device is aimed at preventing mosquitoes and debris from entering the
tank. It includes the same wire mesh used in the walls of tank but here, as a sieve; to remove large
debris. Then, wrapped around the bottom, some cloth/nylon to act as a porous membrane –
allowing water flow, but not silt, dirt or mosquitoes. Combined, these two filters will prevent most
non-microscopic contaminants from entering the tank.
The device is designed to sit in the hole at the top of the tank,
and to be removable when required. Either to remove debris
from the filter or possibly replace the cloth when required.
One of the advantages of this design, is that it can be
constructed with the waste materials from the tank
construction; wire mesh cut-offs and spare cement are all that is
needed to build it.
3.12 Sustainable storage
3.12.1 Life span of Tank
The sustainability of the tank is based on the long working life and minimal damage to the area
around the tank. The tank has a life span of over 20 years; this is due to the construction techniques
used. The material used most susceptible to failure is the bamboo struts; which have a life span of
10 years when they are not in contact with the soil. In our construction, the bamboo is completely
encased in cement which increases the working life of the bamboo. This is achieved by eliminating
Figure 21 - CAD drawing of inlet filter

37. 36
many of the factors that encourage and cause rotting such as exposure to insects and
microorganisms carried in air. The structural integrity of the tank is also a major contributor to the
tanks sustainability. The high factor of safety means the tank can withstand substantial flooding and
other trauma.
The tank is more sustainable than the current clay pots used as they are prone to cracking. The life
span of a clay pot is usually around 10 years which is only half the time of the ferrocement tank. The
mesh reinforcement in the ferrocement makes it highly resistant to crack propagation unlike the clay
pots.
3.12.2 Reducing ground Erosion
Sustainability is also achieved by reducing erosion around the water exit points. All the water exit
points have cement underneath to stop soil erosion from weakening the foundations of the tank.
This reduces the damage caused to the surrounding area of the tank resulting in the foundations
staying solid, due to this; the tank’s resistance to flooding is not diminished over time.
3.12.3 Flood Resistance
The current clay pot method of storage is also very vulnerable to flood damage as with floods of 2-
3m the water pots are often smashed by floating debris or carried away in the rising water. Our
design would ideally be able to withstand such flooding or at least be resistant to the flooding. The
shape of the tank will also be an important design consideration as to reduce impact damage the
tank shape should distribute point loads through the whole structure. The shape should also be a
streamline so the water passes easily round the structure to reduce the force experienced by the
tank. This will reduce fatigue on the structure that will eventually cause flaws and cracks.
3.12.4 Reduced Maintenance
Maintenance on the tank is also minimal which means even when the tank is neglected it stays in
good condition. The design has been made to have very few moving parts to keep this low level of
maintenance. Repairing the tank is also a simple procedure and requires very little cost or skill. If
cracks or weak spots are identified they can be filled with a mix of cement. The repair will need to be
reasonably thick as it will not give the same strength for the same thickness as the original tank due
to the mixes curing at different times.
3.12.5 Locally Sourced Materials
By using locally sourced bamboo and locally manufactured wire mesh the environmental impact of
transporting the materials is reduced. Purchasing or harvesting products from the region, also means
that the money spent purchasing the materials to build the tank, support small local businesses
helping the community as a whole.
3.13 Storage Manufacture
The ferrocement tank has been designed so it can easily constructed by either a single person or a
group of unskilled labourers. This is an essential requirement to keep costs down and give the users
a sense they are building their way to a more hygienic future. The most labour intensive part of the
build is mixing the cement; 1.2m3
is required in total. The maximum recommended amount to be
mixed by hand in the UK is 0.3-0.4m3
per day by a reasonably fit person. This had potential to make
the build unfeasible. The problem is avoided by building the tank in sections. The foundations can be
completed in 1 day the outer and inner walls can be split over 2-3 days and the roof in 1 day. The

38. 37
tank will need to be kept moist over the period of the build to prevent flaws between the dried and
wet mixes. Keeping the tank moist is an essential part of the curing process anyway as the tank
should be allowed to cure over 1-2 weeks to achieve the maximum structural integrity. The Mekong
Delta is an extremely humid region which will naturally aid the curing process; however, the tank will
need to be dabbed with a wet sponge or towel daily as well.
The first draft of an easy to read construction guide can be seen in Appendix B. The intention is to
give the guide to a family in the Mekong Delta that will give them the knowledge to build a more
hygienic water storage solution. A brief overview of the process is given in table 9.
Table 9 - Tank construction process
Step 1 Dig a 10cm deep circle with a diameter of 2.1m
Step 2 Dig a 30cm deep whole where the tap is to be located of oval shape as shown
in the design drawings.
Step 3 Mix 0.32m
3
of cement and pour into the foundation hole. (note any cement laid
should be kept moist with a wet sponge or towel for 2 weeks after laying)
Step 4 Split 25 bamboo poles of 5 cm diameter length 1.6m down the middle and
place them in a circle diameter of 1.975m
Step 5 Split 8 bamboo poles of 5 cm diameter length 1.6m and place them, evenly
spaced, in a line across the centre of the tank. ( there should be a slight slope
to the centre of the tank)
Step 6 Next roll the 1.6m tall wire mesh along the internal bamboo struts( Leaving a
10cm gap at the centre of the tank) and around the external circle of struts
Step 7 Mix and paste cement to a thickness of 5cm over the wire mesh making sure to
place the tap 10cm from the base of the tank, the wash out pipe on the tank
floor and the overflow pipe 10cm below the top of the tank
Step 8 Place 40 split bamboo poles of 5 cm diameter length 1m from the top of the
outer wall onto the centre wall creating a centre hole of 10cm diameter to
allow water entry
Step 8 Place the wire mesh over the roof struts
Step 9 Paste cement over the wire mesh to a thickness of 5cm.
Step 10 Create and place entry system in place at the centre of the tank
3.14 Final Costing
For the final costing the amount of material required and the cost per unit is required. The amount
of material was finalised when the design was completed. The requirements can be seen in the
“Amount required” column and the makeup of each material can be viewed in Appendix A. For the
individual costing, research was undertaken; initially using information provided on the Engineering
without borders website for basic materials progressing to using an in country agent who sourced
prices for more unusual building materials and items.

39. 38
Table 10 - Final tank costings
The target price for the water storage tank was under $80 which is the price currently needed to
store enough water to get a family through the dry season using clay jars. Our design costs $12 less
than this making the tank financially appealing. The tank also has the added incentive of being more
robust, easily accessible and hygienic.
3.15 Storage System Conclusion
To conclude, the ferrocement storage tank is the optimum solution for the rainwater harvesting
problems currently endured by families in the Mekong Delta. As well as fulfilling all essentialities in
the user requirement specifications, the design has the added advantages of being both sustainable
and culturally appropriate to the lives of families in the Mekong Delta.
The improvements that this storage design will have upon the current storage methods adopted in
the Mekong Delta will be invaluable. Firstly the design now has the storage capacity to provide an
average family of 4 with enough drinking and cooking water during the six month dry season.
Furthermore, the storage design is easily adaptable to families of varying numbers through our
construction guide. Secondly the tank has reduced, to a bare minimum, the dangers of storing water
for extended periods of time. By having a closed roof with a removable filtration unit at the tank
entrance we have protected the water from sunlight and air as well as preventing debris and insects
from contaminating the water. Lastly the sustainability of our design ensures that the ferrocement
tank’s longevity far exceeds that of the ceramic storage jars currently installed by many families in
the Mekong Delta; not only can the tank be easily maintained by an unskilled labourer but it can also
withstand the regular damaging floods experienced in the region. Yet perhaps the greatest asset to
the design is its potential to be constructed on site without the need of importing any pre-
manufactured components.
The research conducted into the Mekong region has ensured that all the necessary materials
required to build the ferrocement tank are locally and readily available. This advantage has not only
reduced the financial burden to families but has also afforded them the opportunity to construct the
tank themselves without depending upon specific or bespoke components. The only detriment to
the construction process is the lack of quality control of the final tank. However, this is compensated
by the fact that the stress analysis has given the structural integrity a factor of safety of 30. Such a
high safety factor compared to what is normally acceptable in buildings does allow for the lack of
construction skill. Nevertheless this design is vastly more inexpensive than the price of the cheapest
Material Amount required
Cost per
unit
Individual material cost Total cost
Cement 0.236 m
3
= 354 Kg $0.086 $30.44
$67.81
Sand 0.944 m
3
$7.20 $6.80
Wire mesh 9.65 m (1.6m tall rolls) $1.80 $17.37
Bamboo 82m $0.10 $8.20
Loose key tap 1 $5.00 $5.00

40. 39
equivalent storage method available to families in the Mekong Delta. The table below compares the
prices of the two methods for roughly the same amount of storage capacity
Table 11 - Cost comparison
Storage Method Capacity Total cost for equal storage capacity
Ceramic Jars 1000 litres $80
Group 17 Ferrocement tank 3,600 litres $67.81
Table 12 displays the user requirement specifications previously given on page 21. An additional
column has now been added to confirm the storage design has successfully fulfilled a specific
requirement.
Table 12 - Tank URS check
Category Requirements Status
Functional
Requirements
Must store 3,600 litres of water (900 litres
per person).
Technical
Requirements
Must not allow direct exposure to sunlight.
Materials used must be available locally in
the Mekong Delta.
Tank must be available to build for under
$80.
Implementation and on-site construction
time must be under 2 weeks to allow for
immediate use.
Can be built by an unskilled labourer.
Must safely withstand the internal
pressures of the tank at full capacity.
Operational
Requirements
Water access must have a minimum flow
rate of 7.5 litres/minute.
Tank can be easily maintained by an
unskilled labourer.

41. 40
Water Filtration
Callum Stephen & Nicholas Sidwell

42. 41
4 Filter Solutions
Access to clean drinking water is a basic necessity for humans. Dirty water and poor sanitation kills
over 5000 children every day around the world17
. Reports show that 61% of people living in rural
Vietnam do not have access to clean drinking water; what’s more 80% of diseases in Vietnam are
water borne diseases such as Cholera, Typhoid and Malaria18
. Currently the traditional methods of
water collection involve rivers, ground water and rain water from the roofs of homes stored in large
open topped ceramic jars. The water does not undergo any sort of filtration so diseases are rife.
Contaminated drinking water can cause diarrhoea, cholera and many other diseases. Contamination
occurs mainly from:
 Bacteria: bacteria build up is common in stagnant water
 Viruses: Viruses such as Hepatitis can develop in unfiltered water
 Pollution: Vietnam is a developing country and new industry has resulted in widespread
pollution of the rivers
 Mosquitos: Mosquitos lay their eggs in stagnant water which spreads Malaria
Water borne diseases have knock on effects for families; if one of the parents in a family becomes
unable to work due to illness or death, the children will be required to begin work at an earlier age,
impeding their education. This can have more widespread effects on the country as a whole. If the
occurrence of water borne diseases can be reduced by filtration and education then it will ultimately
help Vietnam to prosper and develop into a More Economically Developed Country.
4.1 User Requirement Specifications
The design concept for the water filtration system is relatively simple; a system must be designed to
take dirty rain water and pass it through a filter so that it is safe to drink for the people of the
Mekong Delta. Currently there is a variety of different water filtration techniques used around the
world but not all of these are viable solutions for Vietnam. Table 13 shows the Musts and Wants for
our water filtration system.
17
http://www.unicef.org/publications/files/UNICEFAnnualReport2004_eng.pdf 26/2/13
18
http://www.ngocentre.org.vn/content/80-diseases-vietnam-caused-polluted-water-resources 27/2/13