Glow-worm
Kettling / water hammer in heat exchanger
Furnace makes loud banging or knocking noises when starting or stopping
Advertisements
Safety Warning
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.
Advertisements
Possible Causes
Limescale build-up in Glow-worm primary heat exchanger, Incorrect pump speed, Air in system, Poor pipe support causing water hammer
How to Fix / Troubleshooting
Safety: Noises can indicate overheating. Monitor pressure and temperature; switch off if in doubt.
User steps:
- Bleed radiators to remove trapped air.
- Ensure system pressure is within the recommended range.
Technician steps:
- Check pump speed setting and adjust to manufacturer’s recommendation.
- Powerflush or chemically descale the primary heat exchanger and system if heavily scaled.
- Inspect pipework for loose clips and secure to prevent banging.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements