BoilerTroubleshooting2026-02-04
Boiler Kettling and Banging Noises Explained
That rumbling 'kettle' sound usually means limescale or sludge in the heat exchanger.
Boilers should run quietly. Kettling, banging or gurgling are signs of build-up or circulation problems worth addressing.
What causes kettling
Limescale or sludge on the heat exchanger causes localized overheating; water turns to steam and the boiler 'kettles' like an old kettle. It reduces efficiency and stresses the unit.
Other noises
Gurgling can mean trapped air (bleed radiators) or low pressure. Banging on start-up can be delayed ignition. A power flush plus inhibitor often cures sludge-related noise.
Key takeaways
- Kettling usually means scale or sludge
- A power flush and inhibitor often resolve it
- Bleed radiators to clear trapped air
- Persistent banging warrants a service
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