Water heater makes loud banging or kettling noises when producing hot water

Safety first: No immediate danger if the appliance is not leaking, but persistent kettling can damage components. Turn off the heater if noises become extreme.

User checks:

• Check system pressure is within the normal range.
• Bleed radiators (if present) to remove trapped air.

Engineer steps:

• Assess the level of scale and sludge in the system and primary heat exchanger.
• Perform a chemical descaling of the heat exchanger or replace it if heavily scaled.
• Flush the system and add inhibitor to prevent future build-up.
• Check pump operation and speed settings.

In hard water areas, fitting a scale reducer on the cold feed can help prevent recurrence.