🚰 NPSH Calculator (Net Positive Suction Head)

Net Positive Suction Head Available

NPSH available is the total suction-side head above the fluid’s vapor pressure at the pump inlet, and must exceed the pump’s required NPSH (from the manufacturer’s curve) to avoid cavitation. It’s calculated as NPSHa = h_a + h_s − h_f − h_vp, where h_a is atmospheric pressure head, h_s is the static suction head (positive if the source is above the pump, negative if it’s a suction lift), h_f is friction losses in the suction piping, and h_vp is the fluid’s vapor pressure head.

If NPSHa drops below the pump’s required NPSH, the fluid can flash to vapor inside the pump, causing cavitation, noise, and damage. Keeping suction lines short, large-diameter, and free of restrictions helps maximize NPSHa. This calculator is for general system-design reference and educational planning.