Water Supply Analysis Calculator

Analyze municipal water supply adequacy using flow test data and N^1.85 curve per NFPA 13/24 hydraulic calculations

Input Parameters

Results

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Available Pressure at Demand
psi
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Pressure Safety Margin
psi
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Max Available Flow at 20 psi
gpm
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Supply Adequacy
Note: Water supply analysis uses flow test data plotted on N^1.85 graph paper. The static-to-residual pressure drop follows the Hazen-Williams friction relationship. NFPA 13 Sec 24.1 and NFPA 24 require supply analysis for all fire protection hydraulic calculations.

Reference

Water Supply N^1.85 Curve (NFPA 13/24): P = Ps - (Ps - Pr) × (Q / Qr)^1.85 Ps = static pressure (psi) Pr = residual pressure at flow Qr (psi) Qr = measured flow at residual (gpm) 1.85 exponent per Hazen-Williams relationship. Maximum flow typically limited to 20 psi residual.