Water distribution

INTRODUCTION:
• After treatment, water is to be stored temporarily
and supplied to the consumers through the network
of pipelines called distribution system.
• The system also includes pumps, reservoirs, pipe
fittings, instruments for pressure measurement,
flow leak detectors etc.
• The cost of distribution is about 40 to 70% of the
total.

REQUIREMENT OF A DISTRIBUTION SYSTEM:
• This should convey the treated water upto
consumers with the same degree of purity
• It should safe against any future pollution. As far as
possible should not be laid below sewer lines.
• Water should be supplied without interruption even
when repairs are undertaken
• The system should be so designed that the supply
should meet maximum hourly demand. For larger
population a peak factor of 2.0 will be adequate.

LAYOUTS OF DISTRIBUTION SYSTEM:
• Dead End or Tree system
• Grid Iron system
• Circular or Ring system
• Radial system

DEAD END OR TREE SYSTEM:
• This system is suitable for irregular developed
towns or cities. In this system water flows in
one direction only.
• The diameter of pipe decreases at every tree
branch.

ADVANTAGES OF DEAD END SYSTEM
• Discharge and pressure at any point is calculated
easily
• The valves required in this system of layout are
comparatively less in number.
• The diameter of pipes used are smaller and hence
the system is cheap and economical

DISADVANTAGES
• There is stagnant water at dead ends of pipes
causing contamination.
• During repairs of pipes or valves at any point
the entire down stream end are deprived of
supply
• The water available for fire fighting will be
limited in quantity

GRID IRON SYSTEM
• From the mains water enters the branches at
all Junctions in either directions into submains
of equal diameters.
• At any point in the line the pressure is
balanced from two directions because of
interconnected network of pipes.

ADVANTAGES
• In the case of repairs a very small portion of
distribution are a will be affected
• Every point receives supply from two directions
and with higher pressure
• Additional water from the other branches are
available for fire fighting
• There is free circulation of water and hence it is not
liable for pollution due to stagnation.

DISADVANTAGES
• More length of pipes and number of valves
are needed and hence there is increased cost
of construction
• Calculation of sizes of pipes and working out
pressures at various points in the distribution
system is complicated.

CIRCULAR OR RING SYSTEM
• Supply to the inner pipes is from the mains
around the boundary. It has the same
advantages as the grid-Iron system.
• Smaller diameter pipes are needed.

RADIAL SYSTEM:
• This is a zoned system. Water is pumped to
the distribution reservoirs and from the
reservoirs it flows by gravity to the tree system
of pipes.
• The pressure calculations are easy in this
system. Layout of roads need to be radial to
eliminate loss of head in bends.

SYSTEM OF DISTRIBUTION:
Depending upon the methods of distribution, the
distribution system is classified as the follows:
• Gravity system
• Pumping system
• Dual system or combined gravity and pumping
system

GRAVITY SYSTEM:
This method is much suitable when the source
of supply such as lake, river or impounding
reservoir is at sufficiently higher than city.
The water flows in the mains due to
gravitational forces. As no pumping is required
therefore it is the most reliable system for the
distribution of water.

PUMPING SYSTEM
• Constant pressure can be maintained in the
system by direct pumping into mains.
• Supply can be effected during power failure
and breakdown of pumps.
• During fires, the water can be pumped in
required quantity by the stand by units.

COMBINED PUMPING AND GRAVITY SYSTEM
• This is also known as dual system. The pump is
connected to the mains as well as elevated reservoir.
• In the beginning when demand is less the water is
stored in the elevated reservoir, but when demand
increases the rate of pumping , the flow in the
distribution system comes from the pumping station
as well as elevated reservoir.
• The water stored in the elevated reservoir meets the
requirements of demand during breakdown of
pumps and for fire fighting.

The water may be supplied to the consumers by
either of the two systems.
1. CONTINUOUS SYSTEM
This is the best system and water is supplied for all
24 hours.
In this system sample of water is always available
for fire fighting and due to continuous circulation
water always remains fresh.
In this system less diameter of pipes are required
and rusting of pipes will be less. Losses will be more
if there are leakages in the system.

2.INTERMITTENT SYSTEM
If plenty of water is not available, the supply of
water is divided into zones and each zone is
supplied with water for fixed hours in a day or on
alternate days. As the water is supplied after
intervals, it is called intermittent system.
The system has following disadvantages:
• Pipelines are likely to rust faster due to alternate
wetting and drying.
• More wastage of water due to the tendency of the
people to store more water than required quantity
and to waste the excess to collect fresh water each
time.
• The repair work can be easily donein the non-
supply hours.

Storage capacity of distribution reservoir
• Balancing(Equalizing) Storage
• Breakdown Storage
• Fire Storage

Water distribution

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