Water heater makes loud banging or knocking noises when burner starts or stops

Safety: Turn off power and water before tightening mounts or adding components.

• Secure pipework: Check that copper or PEX pipes near the heater are properly clipped and not striking walls or the casing.
• Check solenoid valves: If an external solenoid valve is installed, consider adding water hammer arrestors near fast-closing valves.
• Install DHW expansion vessel: In systems with check valves, fit a small potable-water expansion vessel on the hot outlet to absorb expansion.
• Descale heat exchanger: Remove scale that can cause micro-boiling and knocking inside the heat exchanger.