Operator terms · Water and wastewater
What is water hammer?
Water hammer is a pressure surge that happens when flowing water is stopped or started suddenly, such as a valve slamming shut or a pump tripping. The shock can rattle and even burst pipes. Operators open and close valves slowly and use controls to prevent it in distribution and pumping.
Last reviewed 2026-08-03
What causes it
Moving water has momentum. Stop it suddenly and that momentum becomes a pressure spike that travels back through the pipe as a shock.
How operators prevent it
Opening and closing valves slowly, controlling how pumps start and stop, and using surge protection keep the pressure from spiking.
Common questions
- What triggers water hammer?
- Stopping or starting flow suddenly, like a valve slamming or a pump tripping.
- Why is it a problem?
- The pressure surge can rattle and even burst pipes.
- How is it prevented?
- Operate valves and pumps slowly and use surge protection.