Boiler makes loud banging or knocking noises when starting or during operation

Safety first: Turn off power and allow the boiler to cool before touching piping.

• Check system pressure and flow: Ensure the pressure is within normal range and circulators are running. Low flow can cause localized boiling (kettling).
• Bleed air: Air pockets can contribute to noise. Bleed radiators and high points in the system.
• Inspect piping supports: Look for loose or missing pipe hangers that allow pipes to move and bang when heating or cooling.
• Descale heat exchanger: For condensing or copper-tube Burnham boilers, a professional can chemically descale the heat exchanger to remove mineral buildup.
• Adjust fill and expansion: Ensure the expansion tank is functioning and not waterlogged to reduce pressure swings.