Junkers Overpressure / Expansion Control Problem

Water heater frequently shuts off due to overpressure, discharging water from the safety valve.

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

Faulty safety valve, Missing or failed expansion vessel (on storage models), Excessive mains pressure, Non-return valve without expansion relief

Safety: Hot water discharge can cause burns. Do not cap or block the safety valve outlet.

Check discharge pipe: Ensure the pipe from the safety valve is open and directed to a safe drain.
Measure pressure: Have mains pressure checked; install a pressure reducer if necessary.
Expansion vessel: On storage-type Junkers heaters, check that the expansion vessel is present and correctly charged; this is usually a technician task.
Replace safety valve: If the valve drips constantly even at normal pressure, it may need replacement.

Hard 4/5

Safety Valve / Expansion Vessel

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