Pumps are the most important equipment in water supply systems and it consume the greatest amount of energy. Failure of pumping facilities will result in loss of production or supply of water. Planned water quantity and the number of pump units required shall be determined according to the following criteria:
- For treated water pumps the capacity shall be the planned maximum daily delivered quantity and not the average daily quantity. For distribution pump, planned distribution quantity shall be the basis.
- The number of pump units required shall be determined by the planned quantity of water, installation cost, conditions involved in operation and maintenance, power consumption and factor of safety desired.
- It is advisable to use a single duty pump as bigger pumps normally have better efficiency. Parallel pumping may not display its multiplying effect in long pipeline where the frictional losses are significant.
- The following general principles should be applied in the selection of number of pumps installed
- I. Up to 300 m3/hr: 1 duty + 1 standby
- II. Over 300 m3/hr: 2 duty+ 2standby
However all condition should be taken into account (condition of operation, power consumption/efficiency and safety factor desired) and alternatives considered.
- In the case of water demand which fluctuates widely such as in in-line booster distribution systems, it is advisable to have a combination of different sizes of pumps or variable speed pumps
