Quick answer
Banging pipes are water hammer — the shockwave produced when moving water is stopped abruptly and its momentum has nowhere to go. High mains pressure makes it worse, loose pipe clips let the pipe move and amplify it, and fast-closing quarter-turn taps and appliance solenoid valves create it in the first place. It is not just noise: repeated shock loading is what loosens joints and starts leaks.
Common causes
- High mains pressure with no pressure-reducing valve fitted
- Loose or missing pipe clips letting the pipe move inside the wall or ceiling
- No air chambers or hammer arrestors installed on long runs
- Fast-closing quarter-turn taps and mixer cartridges
- Washing machine or dishwasher solenoid valves snapping shut
- Long unsupported copper runs with nothing to absorb the shock
What you can do now
- 1Note which fixture triggers it — a tap, the toilet filling, or an appliance
- 2Tighten any visible pipe clips in the roof space or under cupboards
- 3Close taps more slowly as a test; if the banging stops, it confirms hammer
- 4Measure mains pressure with a gauge on a garden tap
- 5Do not ignore it — repeated shock loading works joints loose over time
When to call a professional
If the banging persists after tightening clips, have a hammer arrestor fitted at the offending fixture, or a pressure-reducing valve at the meter if mains pressure is high. A plumber will identify whether the cause is pressure, support or the fittings themselves, because fitting an arrestor to a system running at 800 kPa treats only the symptom.
Typical cost in Johannesburg
Hammer arrestor + fitting R650–R1,200
Indicative ranges only. We provide written, itemised quotes before any work.
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