The power required to move
water with a pump is called the water horsepower and can be computed by the
following equation:
Water horsepower = Flow
(gpm) x Total Dynamic Head (ft) / 3960
Brake horsepower is the
actual horsepower needed to operate the pump and accounts for inefficiencies
in the pump. Brake horsepower can be obtained by dividing water horsepower by
the pump efficiency, expressed as a decimal:
Brake horsepower = Water
horsepower / Efficiency
Combining these two equations
gives a convenient equation for brake horsepower:
Brake horsepower (pump)
= Flow (gpm) x Total Dynamic Head (ft) / (3960 x Efficiency)
Note that this does not include power
losses within the motor or engine driving the pump.