Heater produces loud banging or knocking noises during operation.

Safety first: Turn off power and gas. Allow the heater to cool before touching any components.

• Check water flow: Ensure the pump is running at full prime and that the filter is clean. Verify all valves to and from the heater are fully open.
• Bleed air: If your Nirvana model has an air bleed valve on the exchanger, open it carefully with the pump running until a steady stream of water (no air) flows.
• Descale exchanger: Kettling is often caused by scale. Have a technician perform a chemical descaling of the Nirvana heat exchanger using approved descaling agents.
• Check gas input (pro): A licensed gas technician should verify that the heater is not overfiring due to incorrect gas pressure or orifice sizing.
• Monitor operation: After corrective actions, run the heater and listen for noise reduction. Persistent banging may indicate internal damage requiring exchanger replacement.