Advice
What Your Combi Boiler's Noises Mean
Learn to read the sounds your boiler makes.
Boilers communicate through sound. A steady hum is normal; new or louder noises usually indicate trapped air, circulation issues or limescale. Learning what each noise means helps you decide whether it's a quick fix or time to call.
This is a companion to our troubleshooting guide — use it to understand the cause before booking a repair.
Decoding the sounds
- Kettling (whistle/rumble): limescale or sludge on the heat exchanger
- Banging at start-up: delayed ignition or air
- Gurgling: trapped air or low pressure
- Humming/vibrating: failing pump
- Clicking before ignition: normal igniter operation
When to call
Persistent kettling, banging on ignition, or any noise paired with a fault code or poor heat should be diagnosed promptly — kettling in particular can damage the heat exchanger over time.
This is not a DIY repair
Combi boilers are gas-fired appliances regulated under the BC Safety Standards Act. Opening the unit, touching the gas valve, or working on the flue without a valid BC gas-fitter licence is both unsafe and illegal. Diagnosing the fault is helpful — fixing it should always be left to a certified technician.
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