Why do my water pipes bang?

Banging can come from loose pipes moving against the building, faulty float valves, a loose stop-tap component, trapped air or a sudden pressure change when a fast-closing valve stops the flow. The sound alone does not identify one universal fix.

Notice when it happens. A bang as a washing machine or dishwasher stops filling points towards a fast valve and a pressure shock. Repeated noise while a cistern fills suggests its valve. Movement from one exposed pipe may indicate poor clipping, but do not cut into walls or floors just to chase a sound.

WaterSafe advises addressing the underlying pressure change because repeated shocks can stress pipework, joints and fixings. It lists pipe supports, the condition of valves and excessive pressure among the points a plumber may assess. A pressure-reducing valve or other control should be selected and set for the system, not guessed.

Do not partly close the main stop tap as a permanent pressure-control method. Record which appliance triggers the noise and whether it affects hot water, cold water or heating pipes, then give those observations to a plumber if it persists.

Make a simple fault diary rather than repeatedly operating valves. Note the room, time, whether a tap was opened or closed, and which appliance had just changed cycle. Check visible pipes for obvious movement without removing floors or panels, and make sure nothing stored in a cupboard is knocking against them. If the banging begins after plumbing work, tell the installer. Noise accompanied by a leak, a visibly moving joint or a sudden pressure change needs prompt professional attention.

A short recording can help a plumber distinguish a single impact from vibration, rattling or a heating-system noise.

Sources

• What causes water pipes banging? — WaterSafe, accessed 14 November 2026.

On Leatmere

Read noisy pipes and water hammer and the water hammer glossary entry.