Ideal Kettling / Local Boiling in Heat Exchanger

Water heater makes loud banging or kettling noises during operation.

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

Limescale build-up on heat exchanger, Sludge in primary circuit, Restricted circulation, Incorrect pump speed setting

Safety: Noisy boiling can indicate overheating. Do not ignore persistent kettling.

Check system pressure and bleed air: Ensure correct pressure (if sealed) and bleed radiators or cylinder coil to remove air.
Verify all valves are open: Confirm that isolation valves on flow and return are fully open.
Water treatment: In hard water areas, arrange for a professional chemical clean or powerflush of the system and descaling of the heat exchanger.
Monitor: If noise worsens or is accompanied by shutdowns, stop using the heater until serviced.

Hard 4/5

Primary Heat Exchanger

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