Kettling
A rumbling sound like a boiling kettle is called kettling. It's usually caused by limescale or sludge building up in the heat exchanger, restricting flow so water overheats and forms steam bubbles. A system clean, descaling or a filter may help.
Other noises
Different sounds point to different issues:
- Gurgling: air in the system or a frozen condensate pipe
- Banging: air, overheating or loose pipework
- Whistling: restricted flow, often from sludge
- Humming or vibration: pump speed or loose fixings
- Clicking without starting: ignition problems
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When to act
If noises are new, loud or come with pressure loss, lockouts or reduced heat, book a Gas Safe registered engineer. Noise is often an early warning of a problem that's cheaper to fix sooner.
