Water Storage

The purification processes deliver clear and clean water at a constant rate. Where as the water consumption varies with time. The hours during which the rate of demand is very high are called peak hours. If there is no storage facility, then all the treatment processes should be designed for higher capacity to meet the rated of demand of peak hours. When storage tank or reservoir is provided, the treatment processes can be installed with a capacity equal to the average rate of demand instead of maximum rate of demand. Thus the sizes of piping system and capacities of pumps in treatment processes also get reduced. In this way storage facility in a water supply scheme leads to an overall economy. The storage tanks also provide buffer capacity, allowing repair and maintenance of parts of distribution system.

After purification processes are over, the water is moved to storage tanks or reservoirs. The capacity of storage structures is after taking in to consideration the peak hour demand and water demand during other eventualities such as fires, break down of pump, etc. The capacity of storage tank also depends on the maximum pumping rate and safe yield of the source of supply. The storage tank may be located at an elevated position or at the ground level. Elevated tanks are installed to obtain pressure head. Water is pumped up in to these tanks. Due to higher elevation, the water in tank will have a pressure head which should be sufficient to overcome the pressure losses in water distribution system.

Material of Construction : Different materials of construction used for storage tanks include masonry, reinforced cement concrete (R.C.C.), plastic, steel and fiberglass. The material should be inert and durable. Tank should be covered properly to prevent evaporation, mosquito breeding and to keep insects, rodents, birds, and children out of reach.

Tanks at ground level are generally constructed with masonry or R.C.C. Elevated tanks could be of steel, plastic or R.C.C. Steel tanks are made by welding steel plates together. The usage of steel tanks for water storage is declining. Pre formed plastic tanks are popular and are used when storage capacity is small. When capacity is big, R.C.C. tanks are the best choice. These have long life, aesthetic appearance and require less maintenance.

Accessories : The major accessories of the storage tanks include the overflow outlet, drain pipe, float switch, man hole and ladder. These are provided to serve different purposes. The over flow outlet is provided to prevent spillage of overflow and connected to a drain. Drain pipe is provided at the bottom of the tank and used for emptying the tank for cleaning or repair. This is also connected to drain. Float switch is activated by float installed near the top of storage tank. When tank is filled up to the capacity the float will move up and switch off the motor to stop the pumping. Provide a manhole for tank inspection and cleaning. Ladder or steps are provided for access of top and bottom of the tank. Vents also may be provided in tanks for air circulation.

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