Boiler makes loud banging or knocking noises when heating starts or stops
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Noisy operation can indicate overheating. Monitor the boiler and be prepared to switch it off if temperatures rise excessively.
Steps to check:
- Bleed system: Remove air from radiators and high points to prevent steam pockets.
- Check flow rate: Ensure all valves are open and the pump is set to an appropriate speed.
- Secure pipework: Inspect visible pipes and secure any that move when the boiler starts or stops.
- Descale heat exchanger: In hard water areas, kettling often indicates scale buildup. A professional can chemically descale or replace the heat exchanger.
When to call a technician: Persistent banging or kettling should be investigated by a heating engineer to prevent damage.
Repair Difficulty
Required Part
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