Saunier Duval
Kettling / boiling in heat exchanger
Water heater makes loud banging or knocking noises during operation
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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.
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Possible Causes
Heavy limescale build-up in primary heat exchanger, Low water flow through heater, Air trapped in heat exchanger, Faulty circulation pump (if fitted)
How to Fix / Troubleshooting
Safety first: Turn off power and gas. Allow the unit to cool before touching pipes or the heat exchanger.
Steps:
- Bleed air: Use bleed valves or automatic air vents to remove air from the system.
- Check flow: Ensure all isolation valves are fully open and inlet filters are clean.
- Descale: Arrange for professional chemical descaling of the Saunier Duval primary heat exchanger.
- Pump check: On models with a pump, verify that the pump is running and not seized.
Warning: Kettling indicates severe overheating in localized areas. Continued use can crack the heat exchanger.
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Repair Difficulty
Hard
4/5
Required Part
Primary Heat Exchanger
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