Pump NPSH Calculator — Available vs Required NPSH | Engineering Calc Pro

💧 Pump NPSH Calculator

Net Positive Suction Head available vs required — prevent cavitation

Atmospheric Pressure (psia)

Fluid Vapor Pressure (psia)

Static Suction Head (ft) negative if below pump

Friction Losses in Suction Line (ft)

Specific Gravity of Fluid

Required NPSHr from pump curve (ft)

NPSHa Available

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NPSH Margin

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Atm Head

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Vapor Head

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NPSHa = H_atm + H_s − H_f − H_vp

H_atm = P_atm / (ρg) | H_vp = P_vp / (ρg)

Cavitation occurs when NPSHa < NPSHr. Minimum margin = 1.0 m (3 ft).

Water pump at sea level, suction tank 5 ft above pump, 3 ft friction losses, NPSHr = 10 ft.

H_atm = 14.7 × 2.31 / 1.0 = 33.96 ft | H_vp = 0.26 × 2.31 = 0.60 ft

NPSHa = 33.96 + 5 − 3 − 0.60 = 35.4 ft → Margin = 25.4 ft ✓

Result: NPSHa = 35.4 ft | Margin = 25.4 ft — SAFE from cavitation