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Pump Sizing For Water Supply Calculator

Work out pump sizing for water supply instantly with clear inputs, formula shown and shareable results.

About Pump Sizing For Water Supply Calculator

Total dynamic head adds three independent requirements: the vertical lift, the friction the pipe imposes and the residual pressure needed at the outlet, converted at 2.31 feet of head per psi. Hydraulic horsepower is GPM x head / 3960, and dividing by pump efficiency gives the shaft power the motor must supply.

Formulas

Total dynamic head

TDH = static lift + friction losses + residual psi x 2.307

Power

WHP = GPM x TDH / 3960; BHP = WHP / pump efficiency

Worked example

With the default values below, Pump Sizing For Water Supply Calculator returns Total dynamic head of 101.1. Change any input above and every figure here is recalculated in your browser.

Inputs used

Design flowminimum 0.1 GPM
25 GPM
Static liftminimum 0 ft
40 ft
Friction and fitting lossesminimum 0 ft
15 ft
Residual pressure requiredminimum 0 psi
20 psi

Results

Total dynamic head
101.1 ft
Hydraulic power
0.638 hp
Shaft power at 65 percent efficiency
0.982 hp
Motor power
0.732 kW

Step by step

  1. 1Values used
  2. 2Total dynamic head
  3. 3Power
  4. 4Total dynamic head= 101.1 ft
  5. 5Hydraulic power= 0.638 hp
  6. 6Shaft power at 65 percent efficiency= 0.982 hp
  7. 7Motor power= 0.732 kW

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Pump Sizing For Water Supply figure worked out?

TDH = static lift + friction losses + residual psi x 2.307. Total dynamic head adds three independent requirements: the vertical lift, the friction the pipe imposes and the residual pressure needed at the outlet, converted at 2.31 feet of head per psi.

Why does the 3960 constant appear?

It folds together the weight of water and the conversion from foot-pounds per minute to horsepower, so GPM and feet of head give horsepower directly for water at standard density.

What values do I need to enter?

This calculator takes 4 inputs: Design flow, Static lift, Friction and fitting losses, Residual pressure required. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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