Navien
Water Hammer / Combustion or Scale Noise
Navien water heater makes loud banging or knocking noises during operation, especially when the burner is firing.
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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 in heat exchanger causing kettling, Sudden valve closures causing water hammer, Loose mounting hardware or piping, Improper gas/air mixture causing combustion rumble
How to Fix / Troubleshooting
Safety: Turn OFF power and gas before opening the unit. Use hearing protection if noise is very loud.
Steps:
- 1. Identify noise source: Listen carefully to determine if the noise is from piping (hammer) or from inside the unit (kettling/combustion).
- 2. Install or check water hammer arrestors: If banging occurs when fixtures close, have a plumber install hammer arrestors near quick-closing valves (e.g., washing machine, dishwasher).
- 3. Descale heat exchanger: Kettling (tea-kettle-like rumble) usually indicates scale. Perform a full descaling flush.
- 4. Check mounting and piping supports: Ensure the Navien unit is firmly mounted and that nearby pipes are properly clipped and not striking walls or studs.
If combustion rumble persists after descaling, a technician should check combustion settings and gas pressure.
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Repair Difficulty
Medium
3/5
Required Part
Primary Heat Exchanger
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