ATAG Water Hammer / Thermal Expansion Noise

Furnace makes banging or knocking noises when starting or stopping

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Rapid valve closure in system, Poorly supported pipework, Excessive temperature differential, Sludge in heat exchanger causing local boiling

Safety first: Allow the system to cool before touching pipework.

Check that all pipework near the boiler is properly clipped and not rubbing against walls or joists.
Reduce the flow temperature setpoint on the ATAG control to lessen thermal shock.
Ensure that any motorised valves in the system are operating smoothly and not slamming shut.
Consider a system flush and inhibitor treatment to remove sludge that can cause kettling and banging.

Medium 3/5