Why is my boiler making banging noises?
Boiler banging (kettling) is almost always caused by limescale or sludge on the heat exchanger. London's hard water makes this a very common issue.
Why is My Boiler Making Banging Noises?
A boiler making banging, rumbling or kettling sounds is one of the most common complaints from London homeowners. The cause is almost always limescale or sludge buildup on the heat exchanger.
What is Kettling?
When limescale or magnetite sludge coats the heat exchanger, water in that section overheats and partially boils — creating steam bubbles that collapse noisily. This is called kettling, and it's particularly common in London due to the city's very hard water.
Other Causes of Boiler Noises
| Noise | Likely Cause | |-------|-------------| | Banging/kettling | Limescale, sludge | | Rumbling | Sludge in heat exchanger | | Whistling | Air in system, pump issues | | Clicking | Ignition (normal on startup) | | Gurgling | Air in pipes or low pressure |
What to Do
- Check boiler pressure — should be 1–1.5 bar when cold
- Bleed radiators — releases trapped air
- Call an engineer — if noises persist, a descale or power flush is needed
Prevention
A magnetic filter (Magnaclean or Fernox) installed in the return pipe captures sludge before it reaches the boiler. RARE fits these as standard on all new boiler installations.
Call our London engineers on 020 7458 4949.
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