Skip to content

PUMP

Water Pump HP Calculator for Overhead Tanks

Work out the pump HP to fill an overhead tank: flow from tank size and fill time, total head from heights and pipe friction, and the right pump size.

Water needed
litres
minutes
Heights and pipe
m

From the water level in the sump or well up to the pump.

m

From the pump up to the top of the tank.

m

Total run from pump to tank.

Assumptions used EDIT ▾
% of pipe

150 for PVC/CPVC, about 120 for old GI pipe.

%

Friction uses the Hazen-Williams formula for smooth plastic pipe, with extra length for bends and valves. Pump power = water flow × total head ÷ pump efficiency; small home pumps are often only 40–55% efficient. A surface pump can lift water only about 6–7 m on the suction side: deeper than that, use a jet or submersible pump. Check the pump's head-and-flow chart before buying.

PUMP SIZE

0.5HP

50 L/min against 17.5 m total head

Total head3 m suction + 12 m delivery + 2.5 m friction
17.5 m
Power neededAt 45% pump efficiency
319 W
Water speed in pipeAbout 1–2 m/s is comfortable
1.50 m/s
Pump0.5 HP

Estimates for planning, based on the assumptions shown. They are not a guarantee of quantities or professional engineering advice; check critical work with a qualified professional.