Service reservoirs, also known as distribution reservoirs, store treated water for supplying water to consumers. There are three types: surface reservoirs built at ground level or below ground; elevated reservoirs which are overhead tanks supported on towers; and stand pipes which are tall cylindrical shells resting on the ground. Distribution reservoirs equalize variations in hourly water demand, maintain pressure in the distribution system, and provide time for disinfection. They have components like inlet/outlet pipes, overflow pipes, and devices to control water levels. The total storage includes balancing storage for meeting fluctuating demand, breakdown storage for emergencies, and fire storage.

2. Service Reservoirs
 It is also known as distribution reservoirs.
These are the storage reservoirs, which store
the treated water for supplying water.
Types of Distribution Reservoir
 Surface Reservoir
 Elevated Reservoir and
 Stand Reservoir

3. Functions of Distribution
Reservoirs
 To equalize the variation in hourly demand of water by the
consumers to a uniform rate of supply from the source
either by gravity or pumping.
 To maintain the desired minimum residual pressure in the
distribution system.
 To provide the required time for the disinfectant added in
order to achieve effective disinfection. And
 To facilitate carrying out repairs either to the pumping or to
pump-set without interruption to the supply of water.

4. Components &
Its Functions
• Inlet pipe for the entry of water.
• Outlet pipe connected to the distribution mains for the exit of
water.
• Overflow pipe discharging into drain gutters and maintaining
constant level.
• A float gauge or an indicator for indicating the depth of water
which can be read from out side.
• a wash-out pipe for removing water after cleaning the
resrvoir.
• Automatic devices to stop pumping when the tank is full.

5. • Ladders to reach the top of the reservoir and then upto the
bottom of the reservoir for inspection.
• Manholes for providing entry into the tank for inspection
purpose.
• Ventilator for freh air circulation

6. Surface Reservoirs
• Surface reservoirs are circular or rectangular tanks
constructed at ground level or below gronund level.
• Therefore they also called as ground reservoirs.
• They are generally constructed at high points in the city.
• In a gravitational type of distributional system. And pumping
system used for treated water is filled the reservoir s.

7. Elevated Reservoirs
 These are the elliptical overhead tanks
erected at a certain suitable elevation
above the G.L and supported on towers.
 They are constructed in the areas
combined gravity and pumping system for
water distribution is adopted.
 Water pumped into these elevated
tanks from the filter units or from the
service reservoirs.
 And then supplied to consumers.
These tanks may be made of R.C.C, steel,
or prestressed concrete.

8. Stand Pipes
• Stand pipes are a kind of elevated tanks without any erected
towers for resting the body.
• They are thus tall cylindrical shells resting directly on the
ground.

9. Storage Capacity
• The total storage capacity of a distribution reservoir is the
summation of :
1. Balancing storage (equalizing/operating storage)
2. Break-down storage And
3. Fire storage
• Balancing storage : The main and primary function of the distribution
reservoir is to meet the fluctuating demand with a constant rate of
supply from the treatment plant. The quantity of water required to be
stored in the reservoir for equalizing or balancing this variable demand
against the constant supply.

10. • Break-down storage : It also called as emergency storage. It is the
storage preserved in order to tide over the emergencies posed by the
failure of pumps, electricity, or any other mechanism drinving the pump.
• Fire storage : The third component of the total reservoir storage. In case
of fires sufficient amount of water must remain available in thereservoir
for throwing it over the fire.