Combined Water Supply + Pump Curve Calculator

Calculate combined water supply and fire pump performance curve to determine total system capacity per NFPA 20

Input Parameters

Results

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Combined Pressure at 100% Flow
psi
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Combined Pressure at 150% Flow
psi
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Total Churn Pressure
psi
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Max Combined Flow at 20 psi
gpm
Note: The combined water supply and pump curve shows total system capacity. The city supply curve (N^1.85) is added to the pump curve point by point. NFPA 20 requires the pump to deliver rated flow/pressure at 100% and not less than 65% rated pressure at 150% flow.

Reference

Combined Supply + Pump Curve: City supply: P = Ps - (Ps-Pr) × (Q/Qt)^1.85 Pump curve: rated Q/P, 150% Q at 65% P, churn at 120% P Combined = city supply pressure + pump net pressure NFPA 20 Sec 4.7: pump must meet 100% and 150% flow points.