Environmental engineering

1. SYSTEM OF WATER SUPPLY
1Prof.C.P.Thosar 9422341867

2.  Distribution of water is the last phase of any
water supply scheme.
 The function of distribution system is to
furnish treated water in required quantity
maintaining its quality under required
pressure wherever it is needed in the city or
town.
2Prof.C.P.Thosar 9422341867

3.  Network of pipes comprising of
 Mains of large diameter
 Sub mains
 Branches
 Feeders or laterals.
 Valves for controlling the flow in the pipes
 Fire hydrants
 Service connection
 Water meters
 Distribution reservoir (Service reservoir)
 Pumps.
3Prof.C.P.Thosar 9422341867

4. 4Prof.C.P.Thosar 9422341867

5.  The following factors or requirements should considered in the
design of distribution system
 It should satisfy all the types of demands including fire demand of
the town.
 It should be capable to meet the maximum hourly flow.
 The manual of government of India has given the following peak
factors according to population:
Sr. No. Population Peak factor
1 Up to 50,000 3.0
2 Between 50,000 to 2 lakhs 2.5
3 More than 2 lakhs 2.0
5Prof.C.P.Thosar 9422341867

6.  The nature of topography of the area occupied by town or
city cannot be expected to be flat.
 It will have natural undulations.
 To know the nature of ground, contour map is prepared by
carrying out contour survey.
 The map will enable the design engineer to divide the city
or town into high level, low level to medium level portions,
with reference to treatment work.
 Such portions or area are called as zones.
 Water in all the zones should be available to tail end
consumer with a minimum pressure of 8 to 10 meters of
water
Prof.C.P.Thosar 9422341867 6

7.  There are two systems of water supply to the
public
1.Continuous system
2.Intermittent system
Prof.C.P.Thosar 9422341867 7

8.  In this system, water is supplied throughout the
day i.e. for 24 hours without any break. When
the water available for distribution is in
abundance, this system is used.
 The system is ideal, since the water is not
remaining stagnant at any time in the pipe-line
and fresh water is always available to the
public.
Prof.C.P.Thosar 9422341867 8

9.  In this system, water is supplied to the public some
fixed hours of the day. Hence, the supply is said to
be intermittent.
 Generally, the water supply 3-4 hours in the
morning as well as in the evening.
 The system is required to be adopted when
sufficient quantity of water is not available or when
sufficient pressure cannot be maintained in the
system.
 Under such circumstances, various zones in the
town are supplied with water by rotation.
 This system is most widely used in India.
Prof.C.P.Thosar 9422341867 9

10.  Following are the four types of systems. They
can be used singularly or in combination as
required by local conditions.
A. Tree or dead end system.
B. Ring or circular system.
C. Grid or interlaced system.
D. Radial system.
Prof.C.P.Thosar 9422341867 10

11.  The layout of pipe-lines resembles the nature of
the tree and hence the name.
 There is one main pipe-line from which number
of sub mains are taken out according to number
of roads.
 The flow thus flows only in one direction through
all pipes till it comes to dead ends. Hence, the
system is suitable for old towns having
unplanned roads and localities having
uncontrolled growth. Such layout is shown in fig.
Prof.C.P.Thosar 9422341867 11

12. Prof.C.P.Thosar 9422341867 12

13.  Merits
 The system is simple, economical and can be
extended according to the growth.
 For controlling flow of water, the number of sluice
valves (also called as cut-off valves) required are less.
 The discharge and pressure head at various points in
the system can be worked out easily.
 Demerits
 For fire fighting, sufficient water may not be available
as only one pipe is supplying water.
 Due to numerous dead ends, water does not have free
circulation which may lead to contamination.
Prof.C.P.Thosar 9422341867 13

14. Prof.C.P.Thosar 9422341867 14

15. Prof.C.P.Thosar 9422341867 15

16. Prof.C.P.Thosar 9422341867 16

17.  Depending upon the topography of the town,
the water may be distributed by
 Pumping
 Gravity
 Combination of pumping and gravity (dual
system)
Prof.C.P.Thosar 9422341867 17

18. Prof.C.P.Thosar 9422341867 18

19. Prof.C.P.Thosar 9422341867 19

20. Prof.C.P.Thosar 9422341867 20

21.  Computation of flow and pressures in networks of
pipes has been of great value and interest for
those involved with the design, construction and
maintenance of public water distribution systems.
 Many methods have been used in the past to
compute flows in networks of pipes. Such methods
range from graphical methods to the use of
physical analogies and finally to the use of
mathematical models.
Prof.C.P.Thosar 9422341867 21

22.  Dead-end method
 Hardy-cross method
 Equivalent pipe method
Prof.C.P.Thosar 9422341867 22

23. Prof.C.P.Thosar 9422341867 23

24. Prof.C.P.Thosar 9422341867 24

25. Prof.C.P.Thosar 9422341867 25

26. Prof.C.P.Thosar 9422341867 26
 This method is applicable to closed-loop pipe
networks.
 The outflows from the system are assumed to occur at
the node(NODE: end of each pipe section.)
 The Hardy Cross method assumes that the flow going
in and out of the system is known and that the pipe
length, diameter, roughness and other key
characteristics are also known or can be assumed.
 The method also assumes that the relation between
flow rate and head loss is known, but the method
does not require any particular relation to be used.

27.  Equivalent pipe is a method of reducing a
combination of pipes into a simple pipe
system for easier analysis of a pipe network,
such as a distribution system.
 An equivalent pipe is as imaginary pipe in
which the head loss and discharge are
equivalent to the head loss and discharge for
the real pipe system.
 There are three properties of a pipe:
diameter, length and roughness.
Prof.C.P.Thosar 9422341867 27