Heater makes loud banging or knocking noises during operation.

Safety: Turn off power and pump, and allow the heater to cool completely before touching plumbing.

• Restore proper flow: Clean filter, ensure pump is running at adequate speed, and verify all valves are open.
• Check internal bypass: Inspect and service the internal bypass and thermal regulator to ensure proper water distribution through the exchanger.
• Assess for scale: If noises persist, the heat exchanger is likely scaled. Professional chemical descaling or exchanger replacement may be required.
• Correct water chemistry: Work with a pool professional to maintain proper pH, alkalinity, and calcium hardness to prevent future scaling.