THE FEUTEX TOOLKIT

Available NPSH from a Reservoir

Estimate available suction head above vapor pressure.

Hydraulics workspace● Runs in your browser

01 Your input

Absolute surface pressurePaAbsolute vapor pressurePaLiquid densitykg/m³Surface elevation above pump datummSuction line head lossm

02 Your result

View or copy raw result data

Result data

FormulaNPSHa=(psurface−pvapor)/(ρg)+z−hsuction.

Sources and model references

https://www.energy.gov/sites/default/files/2026-04/DOE-HDBK-1012-92_VOL3.pdf

Worked example

Inputs

Absolute surface pressure: 101325 Pa
Absolute vapor pressure: 2339 Pa
Liquid density: 998 kg/m³
Surface elevation above pump datum: 2 m
Suction line head loss: 0.5 m

Expected results

Available NPSH: 11.61399089 m
Surface-to-vapor pressure head: 10.11399089 m

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

Enter every input in the labeled units; use measured or independently specified properties.
Check the stated model assumptions before calculating.
Interpret the output as a model estimate and verify it independently for the intended application.

Try this example

{
  "surface": 101325,
  "vapor": 2339,
  "rho": 998,
  "elevation": 2,
  "loss": 0.5
}

Accuracy and scope

Reservoir surface velocity neglected; actual operating margin over manufacturer NPSHr is not determined. Educational engineering estimate only; not structural or safety certification, equipment selection, or operating recommendations.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.