Poolworld
Kettling / Boiling in Heat Exchanger
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
Scale buildup inside heat exchanger, Low water flow, Air trapped in system, Incorrect bypass valve setting
How to Fix / Troubleshooting
Safety first: Turn OFF power and allow the heater to cool before touching plumbing.
- Restore proper flow: Clean the filter, open all valves fully, and increase pump speed if using a variable-speed pump.
- Bleed air: If your system has air bleeders, open them to release trapped air from the heater and high points in the plumbing.
- Check bypass: Adjust any manual bypass valve so that adequate flow passes through the heater per Poolworld recommendations.
- Descale if needed: If noise persists, have a professional perform a chemical descaling of the heat exchanger to remove mineral buildup.
Warning: Persistent kettling can overheat and crack the heat exchanger; address promptly.
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Repair Difficulty
Hard
4/5
Required Part
Heat Exchanger
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