Boiler makes loud banging or knocking noises in the piping when starting or stopping.

Safety first: No immediate combustion hazard, but turn off power if you suspect a leak or structural issue.

• Identify source: Listen to locate whether the noise comes from the Laars boiler, near zone valves, or along piping.
• Check pipe supports: Secure any loose pipes with proper hangers or clamps to prevent movement.
• Slow down closing valves: If you have adjustable zone valves, set them to close more slowly if possible.
• Verify expansion tank: Ensure the expansion tank is properly charged and connected; a failed tank can worsen banging.

When to call a professional: Persistent water hammer may require installation of water hammer arrestors or system balancing by a technician.