Immergas
Chronic Pressure Loss
Boiler frequently loses pressure and needs topping up every few days.
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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
Leak in heating circuit, Faulty expansion vessel (loss of air charge), Leaking pressure relief valve, Micro-leaks in radiators or pipework
How to Fix / Troubleshooting
Safety: Do not repeatedly overfill the system above the recommended pressure. This can cause further leaks.
- Check for visible leaks: Inspect all radiators, valves, and accessible pipework for signs of water or staining.
- Check pressure relief valve (PRV): Look at the PRV discharge pipe outside. If it drips when the boiler heats up, the PRV may be passing due to overpressure or debris.
- Test expansion vessel (engineer): With the system depressurised, measure the air charge at the expansion vessel Schrader valve. Recharge to the value specified by Immergas if low, or replace the vessel if it will not hold pressure.
- Replace PRV if needed: If the PRV has been passing, replace it; once lifted, it often fails to reseal properly.
- Monitor pressure: After repairs, set cold pressure to around 1.0–1.5 bar and monitor over several days.
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Repair Difficulty
Hard
4/5
Required Part
Expansion Vessel
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