Immergas Over-pressurization / Expansion Vessel Failure

System pressure rises rapidly when heating and relief valve discharges water

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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

Expansion vessel lost air charge or bladder failure, Filling loop left open, Faulty pressure relief valve

How to Fix / Troubleshooting

Safety: Hot water may discharge from the safety valve. Keep clear of the discharge pipe.

Steps:

  • 1. Check filling loop: Ensure the filling valve is fully closed and not passing water.
  • 2. Observe pressure behavior: If pressure rises from ~1 bar cold to over 3 bar hot, the expansion vessel is likely not functioning.
  • 3. Technician service: Isolate and check the expansion vessel pre-charge with a gauge. Re-pressurize with air/nitrogen or replace the vessel if the bladder is ruptured. Replace the pressure relief valve if it has been repeatedly lifted and now drips.
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Repair Difficulty

Hard 4/5

Required Part

Expansion Vessel
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