Pump NPSH Available

Atmospheric, vapor, static, and friction heads to NPSHa with cavitation flag.

Run the calculator

Example

You enter

Water temperature (°F) 60
Source elevation vs pump (ft, + above) 5
Suction friction loss (ft) 2
NPSH required (ft, optional) 8

You get

Atmospheric head 33.90 ft
Vapor pressure head 0.59 ft
H friction (ft) 2
NPSH available 36.31 ft

Details, formula, and sources

NPSHa = H_atm + H_static_source − H_friction − H_vapor (all in ft of pumped fluid). H_atm from elevation-lapse; H_vapor from a public engineering psi-by-temperature table converted via 2.31 ft/psi.

Hydraulic Institute by name; ASHRAE Fundamentals water-property tables.

HI standards licensed; vapor-pressure data free at NIST.

Estimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.

Field names used by the API: water_temp_F, source_elevation_relative_ft, friction_loss_ft, npsh_required_ft, H_atm_ft, H_vapor_ft, H_friction_ft, NPSHa_ft

Vapor-pressure table ASHRAE Fundamentals; converted via 2.31 ft H2O / psiASHRAE Fundamentals
Elevation lapse P_atm = 14.696 × (1 − 6.876e-6 × elev_ft)^5.2561ICAO Standard Atmosphere