Protherm Chronic Pressure Loss

Boiler frequently loses pressure and needs topping up every few days

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

Small leak in heating circuit, Faulty expansion vessel losing charge, Pressure relief valve passing intermittently, Micro‑leak in boiler heat exchanger

How to Fix / Troubleshooting

Safety: Allow the system to cool before working on pressurized components.

Steps:

Inspect all radiators, valves, and visible pipework for signs of dampness or staining.
Check the PRV discharge pipe outside for evidence of water discharge; replace the PRV if it is passing.
Test and recharge the expansion vessel to the specified pre‑charge pressure with the system drained; replace if the diaphragm has failed.
If no external leaks are found, a technician should check for internal leaks in the boiler, including the primary heat exchanger.

Repair Difficulty

Hard 4/5

Required Part

Expansion Vessel

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