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Water Hammer (Surge Pressure) Calculator
Enter wave speed and velocity change — surge pressure updates instantly.
Formula
ΔP = ρ · a · Δv (Joukowsky equation)
Typical Wave Speeds a (m/s)
| Pipe material | a (m/s) |
|---|---|
| Steel | 1200 – 1400 |
| Ductile iron | 1000 – 1200 |
| PVC / PE | 400 – 600 |
| Concrete | 900 – 1000 |
Example
Steel pipe (a = 1200 m/s), water flow stopped from 2 m/s: ΔP = 1000 × 1200 × 2 = 2.4 MPa = 24 bar — often enough to burst fittings.
FAQ
What causes water hammer?
Sudden velocity change — fast valve closure, pump trip, or check-valve slam. The kinetic energy converts to a pressure wave.
How is water hammer prevented?
Slow-closing valves, surge tanks/accumulators, check valves with damping, air vessels, or soft pump starts (VFD).