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Originally Posted by Esam

A pump does not completely convert the kinetic to pressure energy. Some of the energy is always lost internal and external in the pump.
Internal losses

• hydraulic losses - disk friction in the impeller, loss due to rapid change in direction an velocities through the pump
• volumetric losses - internal recirculation at wear rings and bushes

External losses

• mechanical losses - friction in seals and bearings

The efficiency of the pump at the designed point is normally maximum and is called the

• Best Efficiency Point - BEP

It is possible to operate the pump at other points than BEP, but the efficiency of the pump will always be lower than BEP.