(a) The normal pumping rate and also the minimum and maximum rate that the pump will be called on to deliver.

(b) Total head capacity to meet flow requirements.

(c) Net positive suction head (NPSH available must exceed NPSH required).

(d) Pump characteristics, including speed, number and spatial, environmental, and other special requirements.

(e) Possible cavitation and vibration problems.

The proper pump must be selected to suit the system conditions. For booster stations with pumped storage, it is desirable that the pressure in the piped water distribution system remain, as much as possible, constant, regardless of the demand on the system. When constant speed pumping units are used, pumps with flat (as opposed to steep) flow vs. TDH performance curves best achieve this condition. However, an extremely flat pump curve may result in an unacceptable large number of start and stop cycles because the flatter the pump performance curve, the more rapid is the approach towards shutoff as system demand is reduced.

Pumps that have an operating point at or near their peak efficiency should be selected. Emphasis on efficiencies is increasing because of high energy costs. Therefore, in order to have pump capacities close to demand (for good efficiency), installation of pumps large enough to handle present and future flows, but with smaller impellers originally which can be replaced by larger impellers as demand grows, may have to be considered.

Other factors previously outlined must also be considered in selecting from the multitude of options available, but meeting the system discharge requirement of reasonable efficiency is paramount. As far as possible, pumps of the same capacity shall be selected.

System head curves, with the pump (pumps) characteristics curves superimposed, showing operating points, and pump performance curves showing range and efficiencies shall be submitted for review and approval. (28-ME-DG-02 § 6.4)