Junkers Water Hammer / Delayed Ignition

Heater makes loud banging or knocking noises when starting or stopping.

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.

Possible Causes

Loose mounting or pipes, Excessive gas build-up before ignition, High water pressure causing pipe movement, Scale in heat exchanger causing micro-boiling

How to Fix / Troubleshooting

Safety: Repeated loud bangs on ignition can indicate a dangerous combustion issue.

Secure pipework: Check that copper pipes around the heater are clipped and not hitting walls when valves open/close.
Check water pressure: Install or adjust a pressure reducer if mains pressure is very high.
Listen to ignition: If there is a noticeable delay between spark and flame, stop using the heater and call a technician to check gas pressure and burner.
Descale: Kettling or popping sounds during operation suggest limescale; arrange professional descaling.

Repair Difficulty

Hard 4/5

Required Part

Primary Heat Exchanger / Burner Assembly

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