Water hammer is a banging or knocking noise occurring in plumbing pipes when water flow stops suddenly, typically when a fast-closing valve, like a washing machine solenoid valve, abruptly halts the moving column of water, creating a pressure shockwave that causes pipes to bang against framing or each other.
This phenomenon becomes more pronounced in homes with higher water pressure or pipes that aren’t adequately secured, since both excessive pressure and loose pipe mounting can amplify the noise and potential vibration this sudden flow stoppage creates.
While occasional, mild water hammer might be merely an annoyance, persistent or severe water hammer can potentially loosen pipe connections or cause premature wear over time, making this issue worth addressing rather than simply tolerating indefinitely.
What Causes Water Hammer?
- Fast-closing valves stopping water flow abruptly
- Excessive water pressure amplifying the shockwave
- Inadequately secured pipes allowing movement
- Missing or failed water hammer arrestors
Why Is Water Hammer Important?
Beyond simple annoyance, persistent water hammer can potentially stress pipe connections and joints over time, making this issue worth addressing through solutions like installing water hammer arrestors, securing loose pipes, or moderating excessive water pressure rather than simply living with the disruptive banging noise indefinitely. Addressing the root cause protects both household peace and the plumbing system’s long-term integrity.
Because water hammer arrestors have a limited service life and can eventually fail, particularly older air chamber style arrestors that can become waterlogged, persistent water hammer despite existing arrestors sometimes indicates these devices need replacement rather than the problem being unsolvable. This straightforward troubleshooting approach typically resolves what can otherwise feel like a persistent mystery noise.
Water Hammer vs. Water Hammer Arrestor
Water hammer is the disruptive noise and pressure shockwave problem itself. A water hammer arrestor is the specific device installed to absorb that shockwave and prevent the resulting noise and potential pipe stress.