Sime
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
System leak on radiators or pipework, Faulty expansion vessel, Pressure relief valve passing, Micro-leaks inside boiler
How to Fix / Troubleshooting
Safety first: Do not repeatedly overfill the system above 2.0 bar; this can cause further damage.
- Inspect for visible leaks: Check all radiators, valves, and accessible pipework for damp patches or staining.
- Check PRV discharge pipe: Look outside at the copper discharge pipe. If it drips when the boiler heats, the PRV is opening.
- Record pressure changes: Note the cold and hot pressures. A large rise when hot suggests a failed expansion vessel.
- Engineer tasks: The engineer should check and recharge or replace the expansion vessel, replace a passing PRV, and pressure-test the system for hidden leaks.
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Repair Difficulty
Hard
4/5
Required Part
Expansion Vessel
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