Water
Water Hammer Pressure Calculator
Estimate water hammer pressure surge from a rapid change in flow velocity using the Joukowsky equation.
Use 0 for complete rapid flow stoppage.
Wave speed depends on water properties, pipe material, diameter, wall thickness and restraint. Use a project-specific value where available.
Optional. Enter the normal static or operating pressure to estimate maximum pressure.
Pressure Surge
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Ideal instantaneous surge caused by the entered change in flow velocity.
Pressure surge
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Pressure surge
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Pressure surge
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Surge head
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Surge head
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Velocity change
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Wave speed
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This is an ideal rapid-transient estimate. Actual water hammer depends on valve or pump closure time, pipe length, pipe elasticity, supports, air pockets, system layout and wave reflections.
Method:
The Joukowsky equation is used:
ΔP = ρ × a × ΔV
where ΔP is pressure change, ρ is water density, a is pressure-wave speed and ΔV is the change in flow velocity.
Equivalent surge head is:
ΔH = a × ΔV ÷ g
This calculator assumes water density of approximately 1000 kg/m³.
The Joukowsky relation represents an essentially instantaneous or sufficiently rapid change in velocity. If valve closure or pump deceleration occurs over a significant time relative to the pressure-wave travel time through the pipeline, the actual transient may be lower and requires a more complete hydraulic transient analysis.
Wave speed should not be treated as a universal constant. It changes with fluid compressibility, pipe-wall elasticity, pipe diameter, wall thickness, restraint and other system characteristics.