Water Hammer Pressure Surge Calculator

Calculate water hammer (hydraulic transient) pressure surge from sudden valve closure in fire protection piping systems

Input Parameters

Results

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Pressure Wave Speed
ft/s
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Surge Pressure Rise
psi
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Critical Closure Time
s
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Severity Assessment
Note: Water hammer occurs during sudden valve closure or pump shutdown. The pressure surge can exceed system rating and cause pipe failure. NFPA 24 Sec 10.8 addresses surge protection. Slow-closing valves (>5× critical time) greatly reduce surge pressure.

Reference

Water Hammer (Joukowski Equation): a = 4660 / sqrt(1 + (K/E)×(D/t)) [wave speed, ft/s] dP = 0.0134 × a × v [pressure surge, psi] Critical time Tc = 2L/a K = 300,000 psi (water bulk modulus) E = 30,000,000 psi (steel modulus) Slow closure reduces surge: dP × (Tc/T_closure)