This document discusses various aspects of water supply schemes including water intake structures, quantity requirements, and components. It describes the different phases of a water supply scheme including source selection, raw water collection and conveyance, treatment, pumping and storage, and distribution. Key factors considered for designing water supply schemes are identified such as population served, water demands, quality requirements, and survey data. Common intake structure types and their factors are outlined. Methods for estimating water quantity needs like domestic, industrial, public and firefighting demands are provided. Population forecasting methods and factors affecting per capita water demand are also summarized.

1. UNIT –II
INTRODUCTION TO WATER SUPPLY SCHEME
a) Introduction to water supply scheme:
b) Water intake structures:
c) Quantity:

2. WATER IS THE BASIC NEED OF ALL LIVING BEING
 NECESSITY OF WATER
 Drinking, cooking, washing, bathing, sanitary purpose.
 Industrial Processes, Steam generation.
 Swimming pools, water games(parks).
 Ornamental displays like fountains.
 Watering lawns, gardens and roads.
 For modern applications such as air conditioners, dish
washers, washing machines etc.
 For extinguishing fires
 Irrigation purposes.

3. WATER SUPPLY SCHEME : VARIOUS PHASES
 Selection of source
 Collection and conveyance of raw water
 Treatment of water
 Pumping and storage of water in ESR
 Distribution of water
DATA TO BE COLLECTED FOR WATER SUPPLY SCHEME
1. Source of water
2. Quantity of water required
- - Population to served
- - Water demands- domestic, public, industrial
- - Design period
3.Quality of water 4. Survey data
5. Map or plan of town or city and
6. Acquisition of land & compensations

4. COMPONENTS OF WATER SUPPLY SCHEME
Water Source
Intake
Structure
Pumping
Unit
Rising/
falling main
Treatment
Units
ESR
Distribution
System

5. LAYOUT OF WATER SUPPLY SCHEME
Source Intake Well Jack Well Aeration
Clarifier
Sand
filter
Disinfection
Distribution
Storage
Tank
ESR

6. DESIGN PERIOD
 Future estimated period of number of years for which
provision is made in designing the capacities of various
components/units of water supply scheme is called as
design period.
DESIGN PERIOD FOR VARIOS COMPONENTS OF WTP
Sr.
No
Components Suggested design
Period
1. Dam, Weir, Intake Structure,
Reservoir, penstock pipe
30 – 35 Years
2. Treatment units- aerator,
clarifier, filter
20 – 30 Years
3. Distribution System
a) Pipe less than 300 mm Dia. 30 Years
b) Pipe More than 300 mm Dia. 20 – 25 Years

7. CONVEYANCE OF WATER
Selection of material for Pipe
 Carrying capacity of the pipe
 Durability of the pipe
 Type of water to be conveyed
 Availability of funds
 Repair and maintenance cost
Types of Pipes
1.Cast iron: Available in length of 3-6m
Advantages: Moderate cost
highly resistant to corrosion,
Strong,, easy jointing,
withstanding high internal pressure
long life (100 Yrs.)
Service connections easy

8.  Disadvantages :Very heavy and difficult to transport,
brittle easily cracks, cannot used for pressure more than
7 kg/cm2. they are fragile (delicate ).
2. Steel pipe: Made from steel bars, by hot or cold process.
mostly used for main lines where pressure is high and
diameter requirement is more.
Advantages: strong, light weight and withstand higher
pressure than cast iron pipes, cheap, easy to construct and
can be easily transported.
Disadvantages: Cannot withstand external loads,
affected by corrosion,
difficult to make connections,
and maintenance are costly.

9. 3. Cement lined Cast Iron Pipes: Mortar lining of 1:1
proportion is applied . Thickness of lining 5 – 6 mm.
Advantages: more life, Easily constructed on site and
factories, least coefficient of expansion, not affected by
force of buoyancy.
Disadvantages : Repairs are very difficult, difficult to
make connection, due to heavy weight transportation and
laying costs are high.

10. 4. Plastic Pipes: Made from synthetic resins of high
molecular weight. Polymerized from simple compounds by
heat, pressure and catalysis. Plastic pipes and tubes are
manufactured from a number of polymerization products
such as polythene, polypropylene,, poly vinyl chloride and
cellulose acetate butyrate.
Advantages - corrosion resistant , light weight and
economical, Cheaper, easy to handle and transport, good
electrical insulators, adequate strength, durable and
unaffected by weather.
Disadvantages :
Coefficient of
expansion is high,
low resistance to heat.

11. 5.Wrought iron and galvanized iron pipes: Manufactured
by rolling flat plates of wrought iron to the proper
diameter and welding the edges. These pipes are
usually protected by coating them with a thin film of
molten zinc. Easily cut, threated, lighter in weight. More
costly , less durable.
6. Cement concrete pipes: PCC up to heads of 7m.
RCC up to head of 60m. For higher heads prestressed
concrete pipes are sed.
NP1,NP2,NP3 – non-reinforced or non-pressure pipes.
used for drainage lines, irrigation etc.
P1,P2,P3 – Reinforced concrete pipes. Pressure they
withstand may be 2.0 kg/cm2(20 m), 4.0 kg/cm2 (40m)
and 6.0 kg/cm2(60m).

12. Advantages: resists the external loads and backfill
loads, maintenance cost is less, no corrosion, pipe can be
cast at site, no transportation cost. No expansion joints.
Disadvantages: Tensile cracks, leakage problem ,
repair is difficult, handling is difficult.
7. Copper and lead pipes: made from copper and lead,
costly, soft and bend easily

13.  VALVES: various appurtenances are use to isolate and drain pipe
sections for test, installation, cleaning and repair.
 Valves are one of the important device provided to stop and regulate
the flow of water in the course of ordinary operations and in an
emergency.
VALVES ARE USED TO SERVE THE FOLLOWING PURPOSES:
 To control the rate of flow of water
 Release or admit air into the pipeline
 Prevent or detect the leakage
 Meet the demand during emergencies
 Make the distribution system more efficient.
FACTORS CONSIDERED IN THE SELECTION OF VALVES:
 purpose and operation,
 capacity required,
 head loss and rate of flow,
 cost,
 availability, etc.

14. TYPES OF VALVES
 Sluice or gate valve
 Air relief Valve
 Reflux valve
 Relief valve
 Altitude
 Score Valve
SLUICE VALVE: These are also known as gate for stop
valve. They are used in distribution system. Spacing of
these valves may be between 150 to 300 meters. Also
placed at street corners or where two pipelines intersects.
 AIR RELIEF VALVE: Air relief valves are installed at
high points of distribution piping to provide an exit for
entrapped air. They are also used to discharge air when
a main is being filled and to admit air when it is being
emptied.

15. REFLUX VALVE: It is also known as check valve or Non-
return valve. This valve allows the water to flow in one
direction only. They are placed in water pipes which
obtain water directly from the pump. when the pump is
stopped ,they the in the pipe dose not rush back and
damage the pump. It consists of flat disc, pivoted so that it
is forced open when flow of water is in one direction and
forced shut against a seating when flow tries to reverse.
PRESSURE RELIEF VALVE: also known as automatic
cutoff valve or safety valve. They are located at those
points where pressure is likely to be maximum. When
pressure in line increases above preset value, the valve
operates automatically, and the pressure is reduced.

16.  ALTITUDE VALVES : These valves are mainly used
on those lines which supply water to elevated tanks
or stand pipes, to automatically control the flow into
and out of an elevated storage tank or standpipe to
maintain desired water level elevations. These valves
close automatically when the tank is full and open
when the pressure on pump side is less than on the
tank side of the valve.
 SCORE VALVE: Also known as blow off or washout
valve. Located either at dead ends or at lowest points
in the mains. Provided to remove the sand and grit
deposited in the pipelines.

19. INTAKE STRUCTURES
 Intake structures are the structures used for admitting
water from the surface sources and conveying it further
to the treatment plant. It is masonry or concrete
structure with an aim of providing relatively clean
water, free from pollution, sand, grit and objectionable
material.
Factors Governing Location of Intake
 As far as possible, the site should be near the treatment
plant so that the cost of conveying water to the city is
less.
 The intake must be located in the purer zone of the
source to draw best quality water from the source,
thereby reducing load on the treatment plant.
 The intake must never be located at the downstream or
in the vicinity of the point of disposal of wastewater.

20.  The site should be such as to permit greater
withdrawal of water, if required at a future date.
 The intake must be located at a place from where it
can draw water even during the driest period of the
year.
 The intake site should remain easily accessible
during floods and should not get flooded. Moreover,
the flood waters should not be concentrated in the
vicinity of the intake.
 It should have good foundation, further expansion can
be possible, river flow should not get obstructed.

21. TYPES OF INTAKE
Submerged Exposed Wet Dry
Constructed
entirely
under water.
Such intake
are used to
get supply
from lake.
It is in the form of
tower or well
constructed near
bank of river or
away from bank.
These are very
common due to
ease in its
operation.
A wet intake is
that type of
intake tower in
which the
water level is
practically the
same as the
water level of
the sources of
supply.
There is no
water in the
water tower.
Water enters
through port
directly into the
conveying
pipes. The dry
tower is simply
used for the
operation of
valves.

22.  River Intake
 Reservoir Intake
 Lake Intake
 Canal Intake

28. INTAKE STRUCTURES

31. VARIOUS TYPES OF CONSUMPTION/DEMANDS
 Domestic consumption
 Industrial and commercial demand
 Public demand
 Fire fighting demand.

32.  Domestic consumption: the water required for
actual household activities is known as domestic
demand. It includes water required for drinking,
cooking, bathing, washing flushing of toilets etc.
Details of Domestic consumption
Purpose Water consumption
( lit/capita/day)
Drinking
Cooking
Cleaning of utensils and
house
Washing of clothes
Flushing of water
closets(W.C.)
Bathing
TOTAL
5
5
20
20
30
55
135

33.  Industrial and Commercial Demand: Industry requires large
quantity of water for manufacturing, cooling operation, steam
generation, for processing and sanitation. This is known as
industrial demand. Commercial demand includes water required
for private offices, restaurants, cinema halls motor garages and
small scale industries. This demand can be expressed per capita
demand ,by dividing the industrial demand by the population of
the area.
Details of Industrial and commercial Demand
ACTIVITY DEMAND(lit/capita/day)
Factories
Offices
Restaurants/seat
Hotels/person
Cinema/seat
30-45
45
70
180
15

34.  Public Demands: It includes water required for
washing of roads, cleaning of public sewers, watering
of parks, gardens water fountains, swimming pools,
flushing of water closets and urinals, hospitals, hotels,
schools and colleges. This demand is about 5
percentage of total demand.
Details of Public Demands
ACTIVITY DEMAND
Public gardens
Street washing
Sewer cleaning
Hospitals
Hotels
Schools(without boarding)
Schools(with boarding)
1.4 lit/m2/day
1.0 lit/m2/day
4.5 lit/head/day
340 - 450 lit/bed/day
135 lit/head/day
45 lit/head/day
135 lit/head/day

35. FIRE FIGHTING DEMAND

36. FACTORS AFFECTING PER CAPITA DEMAND
IN A COMMUNITY
 People's habits
 Industrialization
 Public Services
 Climatic conditions
 Systems of water supply
 Meter system
 System of drainage
 Availability of supplementary sources
 Distribution pressure
 Cost of water

37. POPULATION FORECASTING
1. Arithmetic Increase Method:
 This method is generally applicable to large and old
cities.
 In this method average increase of population per
decade is calculated from the past records and added to
the present population to find out population of next
decade.
 This method gives a low value and is suitable for well
settled and established cities.
Pn = P + n x i
Pn = Population after n decade
P = Present population, n = Nos of decades
i = Average increase in population

38. 2. GEOMETRIC INCREASE METHOD
 In this method percentage increase in population from
decade to decade remains constant.
 Therefore, the average value of percentage increase in
population is calculated and the future population are
calculated at this rate.
 This method gives much higher value and mostly
applicable for growing towns and cities having vast scope
for expansion.
Pn = P( 1 + r/100)n
Where r = Average percentage rate of population increase
P = Present population
Pn = Population after n decade

39. 3. INCREMENTAL INCREASE METHOD
 This method is the combination of arithmetic increase
method and geometric increase method.
 Hence ,combines the advantages of both methods and
gives satisfactory results.
 In this method, average increase per decade is first
calculated and to this average of net incremental
increase once for every future decade is added.
Pn = P + n x i + n(n + 1)/2 x I
Where I = Average incremental increase
i = Average increase per decade
n = Nos of decades

40.  Decreasing rate of increase method
 Graphical comparison method
 Graphical extension method