Net Positive Suction Head Calculator

NPSH (Net Positive Suction Head) is a term referring to fluid supply in a pumping system. NPSH Required (NPSHR) is the amount of fluid that a pump will require at a certain operating point. NPSH Available (NPSHA) is the amount of fluid that a system can deliver to the pump. If NPSHR is greater then NPSHA, meaning the pump requires more fluid than is available to be pumped, the fluid will begin to cavitate and cause damage to the pump. This NPSH calculator is designed to calculate NPSH Available from a system. Fill in the fields below and press “Calculate” to see the results.

Note: In the case of calculating NPSHA for a reciprocating pump, this calculator does not include calculations for Acceleration Head. A pulsating flow on the supply of a reciprocating pump will affect the calculations below. Additional margin should be built into the calculation, as well as adequate pulsation control equipment installed on the suction side of the pump.

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What type of fluid supply system do you have?


Fluid Parameters


Piping System

{{data.hzFrictionCoeff}} Hazen William Coeff.
Add Fitting
{{fitting.Qty}} X
Friction Loss Calculator Piping Example with Valve and Strainer
Calculate Clear All

NPSH Calculator Results

{{result.NPSH}} {{data.RequestedNPSHUnits}}
{{result.FrictionLoss}} {{result.FrictionLossUnits}} ({{result.FrictionLossMethod}})

Explanation: To calculate NPSH Available, take the source pressure {{data.supplyPressure}}, add the atmospheric pressure {{data.atmosphericPressure}}, subtract the losses from friction within the pipeline {{result.HazenWilliams}} and subtract the vapor pressure of the fluid {{data.vaporPressure}}. The result equals the NPSHA (or Net Positive Suction Head Available) of your system. The Net Positive Suction Head Required by the pumps, referred to as NPSHR, must be LESS THAN the NPSHA of the system, else the pump will cavitate.

Note: Because calculating NPSH is complicated and difficult, Power Zone Equipment recommends having a safety factor of at least 150%. If more detailed NPSH calculations are needed, contact the Power Zone equipment engineering team for further assistance.

Important Note: If you are calculating NPSH for a reciprocating pump, do not overlook Acceleration Head. Inadequate pulsation dampening equipment on the suction side of a plunger pump will result in severe cavitation, even if the results above show that NPSHA of the system exceeds NPSHR of the pump.

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