Is it water hammer?
- One sharp bang the moment a lever tap snaps shut.
- A shudder in the wall when the washing machine or dishwasher stops filling.
- A knock as the toilet cistern finishes refilling.
- Thumps in the pipes when the irrigation switches off.
Other pipe noises
| Likely cause | Where to look | |
|---|---|---|
| A single bang as water stops | Water hammer | Quick-closing taps and appliance valves |
| A hum or whistle while a tap runs | A worn washer or valve, or high pressure | The tap itself, then the pressure |
| Ticking as hot water runs | Pipes expanding as they warm up | Hot pipes clipped too tightly |
| A long rattle while the cistern fills | A worn cistern inlet valve | The toilet: see running toilets |
| Gurgling from drains | Air in the waste pipes, or a part blockage | The drains: see blocked drains |
Why it's worth fixing
Each bang sends a shock through the pipes. Over time that can loosen clips and joins, wear out tap and appliance valves, and split flexible hoses, which is how a noise turns into a burst pipe.
What a plumber will do
A plumber will measure the water pressure first, because high pressure makes water hammer worse, and fixing it often fixes the noise. Then they find which fixture sets it off and look at the pipe behind it.
The usual fixes are clipping loose pipe so it can't move, fitting a water hammer arrestor near the valve that slams shut, fitting or replacing a pressure reducing valve, or replacing a worn cistern valve or tap part.
What changes the job
Whether one fixture causes it or the whole house bangs. Whether the pipes are reachable under a timber floor or hidden in walls and slabs. The pressure, and whether a reducing valve is already fitted. And whether the arrestor has to go behind an appliance that needs moving.
Tracking it down
You can
- Work through each tap and appliance to find which one sets it off.
- Close lever taps more gently.
- If you can safely get under the house, look for pipes that are loose or knocking against timber.
- Turn off the isolation valve to a noisy cistern until it's fixed.
Leave to a licensed plumber
- Re-clipping pipes in walls and under floors.
- Fitting water hammer arrestors.
- Fitting or replacing a pressure reducing valve.
- Replacing cistern inlet valves and tap cartridges.
Rules that apply
Valve and pipe work on the water supply is for a licensed plumber. In Tasmania, a business can't carry on as a plumbing contractor without a contractor licence. WA's homeowner list lets you repair a tap yourself, but not a thermostatic mixing tap, and anything beyond the list is a plumber's job there.
Ask whether your job needs a certificate in your state: see compliance certificates.
Questions to ask the plumber
- What's the water pressure here, and is it too high?
- Which fixture is causing it?
- Would an arrestor or a pressure reducing valve fix it, or both?
- Are any pipes or joins already damaged from the banging?
What we would do
Find the fixture that sets it off before you call: it saves the plumber time and narrows the fix. If the whole house bangs, ask for a pressure reading before anything else, because a pressure reducing valve can quiet every tap at once. A plumber who does pressure and pipe work will know which fix suits your house.