Fire Pump NPSH Calculator

Calculate Net Positive Suction Head available (NPSHa) for fire pump installations per NFPA 20 to prevent cavitation

Input Parameters

Results

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NPSHa
ft
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Vapor Pressure Head
ft
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Atmospheric Pressure Head
ft
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NPSH Safety Margin
Note: Net Positive Suction Head Available (NPSHa) must exceed the pump required NPSH (NPSHr) to prevent cavitation. NFPA 20 Section 4.18 requires NPSHa evaluation at 150% of rated flow. Typical fire pump NPSHr ranges from 10-30 ft.

Reference

NPSHa = h_atm + h_s - h_f - h_vap h_atm = atmospheric pressure head (ft) h_s = static suction head (ft, positive if above pump) h_f = friction loss in suction piping (ft) h_vap = vapor pressure head (ft) NFPA 20 requires NPSHa > NPSHr at 150% rated flow.