Pipes Bang When a Tap Is Turned Off

Identify the tap(s) that cause the bang. Quarter-turn ceramic disc taps are the main culprit because they close in a single turn rather than gradually like older washer taps.

Check the water pressure — high mains pressure (above 4 bar) significantly worsens hydraulic shock. A plumber can fit a pressure reducing valve (PRV) to bring pressure down to 2.5–3 bar, which often eliminates the problem entirely (£60–150 for parts and fitting).

Check whether pipe work in the void spaces (under floors, in walls) is properly clipped and supported. Pipes that are loose can move and bang against joists when shock waves pass through. Clip any accessible loose pipes with appropriate pipe clips.

Fit an air chamber or hydraulic shock arrestor on the supply pipe near the worst-affected tap — these are small capped extensions or spring-loaded devices that absorb the pressure spike. Available from plumbing merchants for £10–40.

For washing machines and dishwashers (which use solenoid valves that close instantly), a dedicated shock arrestor fitted to the supply hose connection eliminates the bang for these appliances specifically.

If the bang happens repeatedly and is getting worse, have a plumber inspect the pipework — progressive loosening of compression fittings from hydraulic shock can eventually cause leaks.