Why does it only happen with the washing machine?

Appliance fill valves are solenoids that close almost instantly, which is exactly what creates hammer. Taps close gradually and rarely produce the same shock.

Is a water hammer arrester worth fitting?

Where the noise comes from one appliance, yes — it gives the pressure shock somewhere to go and is a small, local job. Where the whole house hammers, the pressure itself is usually the better thing to address.

My pipes tick when the heating comes on — is that the same?

No. Ticking or creaking on warm-up is pipe expansion rubbing against a clip or a notched joist. It is fixed by freeing the pipe, not by changing pressure.

Could banging pipes burst something?

Not in one bang, but repeated hammer fatigues joints over time and is a known contributor to later leaks. It is worth curing rather than tolerating.

Low risk

Updated 30 August 2026

Banging Pipes

A bang, knock or shudder runs through the pipework when a tap or appliance valve shuts.

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What's happening?

The classic bang as a tap closes is water hammer. Moving water has momentum, and when a valve shuts quickly the column of water stops against it and sends a pressure shock back along the pipe, which the pipe then transmits into the joists and walls as a thump. Washing machines and dishwashers cause it most because their solenoid valves snap shut in milliseconds. A different noise — a slow ticking or creaking as heating warms up — is not hammer at all but pipes expanding against a tight clip or a notched joist, and needs a different fix.

What usually causes it?

Fast-closing solenoid valve on a washing machine or dishwasher shutting against full mains pressure
Loose or missing pipe clips letting a run move and strike a joist or wall when the shock arrives
High incoming mains pressure with no pressure-reducing valve
Air trapped in the pipework after the system was drained down
A failing tap washer chattering against its seat as it nearly closes
Pipes run too tightly through joist notches, so thermal movement grinds rather than slides
A ballvalve in a tank bouncing on its seat as the level nears the shut-off point

Is it dangerous?

Not immediately, but repeated hammer is a mechanical load on every joint in the system and is a recognised cause of long-term joint failure — the split that eventually turns into a leak often follows years of banging. It is worth treating as wear rather than a quirk, particularly in a house with soldered copper and older compression fittings.

Can I fix it myself?

Narrow it down first: run each tap and each appliance separately and note which one causes the bang, and whether it happens on opening or closing. Turning an appliance's isolating valve down slightly so it fills a little more slowly often removes the hammer entirely. Where you have access to exposed pipework in a cupboard or under floorboards, adding or tightening clips stops the pipe striking timber. Do not pack a noisy pipe tight into a notch — it needs to be held but free to expand.

When should you call a plumber?

Call a plumber when the noise is in inaccessible pipework, when it happens throughout the house rather than at one appliance, or when a pressure-reducing valve or arrester needs fitting. Also call if the banging started after other plumbing work, which usually means trapped air or a clip that was never replaced.

What will the plumber actually do?

Identify the source outlet and whether the noise is hammer, expansion or a chattering valve
Measure mains pressure and fit or adjust a pressure-reducing valve where it is high
Fit a water hammer arrester close to the offending appliance valve
Re-clip loose runs and free pipes that are binding in joist notches
Purge trapped air from the pipework and refill correctly
Replace worn tap washers or a bouncing float valve where those are the source

Frequently asked questions

We’re happy to answer all your questions.

Sources & References

Low Water PressureLow risk Dripping TapLow risk Boiler Kettling Or BangingCaution Overflow Pipe Dripping OutsideCaution

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