Baxi Kettling / Water Hammer in Primary Circuit

Furnace 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 build-up in primary heat exchanger, Rapid temperature rise due to poor circulation, Air in system, Loose pipework causing water hammer

Safety: Allow the system to cool before touching pipes or the heat exchanger.

Bleed system: Remove trapped air from radiators and automatic air vents.
Check pump speed: If the Baxi pump has adjustable speed, ensure it is set appropriately for the system size.
Secure pipework: Inspect accessible pipes and secure any that move or bang against walls or joists.
Descale: A professional can chemically descale the primary heat exchanger to remove limescale that causes kettling.

Hard 4/5

Primary Heat Exchanger

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