How do I stop noisy pipes and water hammer?
Diagnosing banging, humming and creaking pipes, and the fixes for each — from clipping loose pipework to fitting an arrestor.
- Difficulty
- intermediate
- Time
- 1 hr 30 min
- Read
- 2 min
Short answer
A bang when a tap or appliance shuts off is water hammer, caused by the sudden stop of moving water — the fix is an arrestor or reducing the pressure. A rattle or knock while water runs is usually loose pipework that needs clipping. Creaking as heating warms up is normal expansion.
Pipe noise sounds alarming and is usually harmless, but it tells you something specific depending on when it happens. Diagnosing it is entirely about noting whether the noise occurs when water starts, while it runs, when it stops, or when the heating comes on.
What you'll need
- Pipe clips
- Screwdriver
- Foam pipe insulation
- Water hammer arrestor (optional)
- Pressure gauge (optional)
Step by step
- Note exactly when the noise happens.On shut-off: water hammer. While running: loose pipe or high pressure. On heating up: expansion. Each has a different fix.
- For a bang when a tap or washing machine shuts off, that is water hammer.The moving column of water stops suddenly and the shock travels through the pipework.
- Check your mains pressure — very high pressure makes hammer much worse.A pressure-reducing valve on the incoming main is the systemic fix if pressure is unusually high.
- Fit a water hammer arrestor near the offending appliance or tap.It contains an air cushion that absorbs the shock. They screw onto the supply and are straightforward.
- For rattling while water runs, find and clip the loose pipe.Follow the noise. Pipes under floors and in airing cupboards are usually the culprits.
- Pack pipe clips with felt or foam rather than clamping metal to metal.A rigid clip transmits noise into the structure. A slightly cushioned one absorbs it.
- For creaking as the heating warms, insulate where pipes pass through joists.That noise is expansion and is normal. Foam or felt where the pipe rubs the timber removes it.
- For a humming or whistling tap, check the aerator and the valve.A partly closed valve or a worn washer commonly causes a whistle at certain flow rates.
Tips
- Water hammer got noticeably more common with quick-closing solenoid valves in washing machines and dishwashers — those are the usual sources.
- Persistent severe hammer can loosen joints over time, so it is worth fixing rather than tolerating.
- If the noise started suddenly with no change to the plumbing, check whether a pressure-reducing valve has failed.
Common mistakes
- Clamping pipes rigidly to fix rattling — Metal-to-metal contact transmits noise into the structure rather than absorbing it.
- Assuming all pipe noise is a fault — Creaking as heating warms is thermal expansion and is normal.
- Ignoring severe water hammer — Repeated shock loading can loosen joints and eventually cause leaks.
Questions people ask
What causes banging pipes when I turn off a tap?
Water hammer — the moving column of water stops abruptly and the shock travels back through the pipework. An arrestor near the source absorbs it, and reducing excessive mains pressure helps.
Is creaking central heating pipework a problem?
Usually not. It is thermal expansion as the pipes warm and rub against joists. Padding where the pipe passes through timber removes the noise.