From a fire pump’s flow rate and head, work out the hydraulic power and the motor power it needs — a starting point ahead of a full pump selection to AS 2941.
Indicative hydraulic power only. Fire pump selection must follow the relevant standard (e.g. AS 2941) and allow for motor sizing margin, pump curves, NPSH and the system’s actual demand.
traqR keeps pump details, block plans and AS 1851 test records against the site so pump inspections don’t slip.
Start free trialA pump’s hydraulic power comes from how much water it moves (flow) and how hard it has to push (head or pressure).
Hydraulic power in kW is flow (L/s) × head (m) × 9.81 ÷ 1000 — the useful power delivered to the water.
No pump is perfect, so the shaft (motor) power is the hydraulic power divided by pump efficiency. Motor selection then adds margin on top.
Hydraulic power (kW) equals flow in litres per second times head in metres times 9.81, divided by 1,000. Divide that by the pump efficiency to get the shaft power the motor must provide. For 20 L/s at 70 m head and 65% efficiency, that’s about 13.7 kW hydraulic and 21 kW at the shaft.
Head is the total height and pressure a pump must overcome, expressed in metres. It combines the static lift, friction losses in the pipework, and the residual pressure required at the most remote outlet. One metre of head is roughly 9.81 kPa.
Because of pump inefficiency and the need for margin — the pump may run at different points on its curve, and the motor must not overload. Fire pumps are selected against a duty point with allowance for these factors under the relevant standard.
No. It gives indicative power only. Fire pump selection and installation must follow the applicable standard (such as AS 2941), using manufacturer pump curves, NPSH, the verified system demand and correct margins, designed by a competent engineer.
This calculator gives indicative hydraulic and shaft power only and is not a substitute for fire pump design to the relevant standard (such as AS 2941). Pump and motor selection must account for pump curves, NPSH, duty margins and verified system demand, by a competent engineer, with maintenance to AS 1851.
traqR keeps pump details, block plans and AS 1851 test records against the site. Try it free for 14 days.