Immergas Expansion Vessel Failure / Overpressure

Water heater's pressure gauge rises when heating and then discharges water from the safety valve.

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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

Loss of air charge in expansion vessel, Undersized expansion vessel, Faulty safety valve, Constantly open filling loop

How to Fix / Troubleshooting

Safety: Allow the system to cool before relieving pressure.

  • Check filling loop: Ensure the filling loop valves are fully closed and not letting water in continuously.
  • Test expansion vessel: With system pressure at zero, measure the air charge at the vessel Schrader valve. Recharge to the specified pressure if low, or replace the vessel if the diaphragm has failed.
  • Replace safety valve if dripping continuously: If the valve continues to leak even at normal pressure, it may need replacement.

Note: Expansion vessel work often requires draining and refilling the system; consider using a professional.

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Repair Difficulty

Hard 4/5

Required Part

Expansion Vessel
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