How to Fix / Troubleshooting

Safety first: Turn off the boiler and allow it to cool before touching pipework.

Check system pressure and flow: Ensure the system is correctly pressurised and that all isolation valves around the boiler are fully open.
Adjust pump speed: If the pump has selectable speeds, increase to a higher setting to improve flow.
Flush system: Consider a chemical flush of the heating system to remove sludge, followed by fitting a magnetic filter.
Descale heat exchanger: In hard water areas, the primary heat exchanger may need descaling or replacement by a professional.

When to call a professional: Persistent kettling usually requires specialist cleaning or replacement of the heat exchanger.

Boiler makes loud banging or knocking noises (kettling) during operation.

Possible Causes