IVT Kettling / Hydraulic Shock

Boiler makes loud 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

Limescale in primary heat exchanger, Incorrect pump speed, Air in system, Poor pipe support causing water hammer

Safety: No immediate danger in most cases, but turn off the boiler if noises are violent or continuous.

Steps:

Check system pressure and top up to the recommended level.
Bleed radiators and high points to remove trapped air.
Adjust the pump speed to a lower or higher setting to see if noise reduces.
A technician can dose the system with a descaling/cleaning chemical and flush to remove limescale and sludge from the heat exchanger.
Ensure pipework is properly clipped to reduce water hammer.

Medium 3/5

Primary Heat Exchanger

Check Price on Amazon

We may earn a commission from links on this page.