Alpha
Chronic Pressure Loss
Boiler frequently loses pressure and needs regular topping up.
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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
Leaking radiator or pipework, Faulty pressure relief valve, Failed expansion vessel, Micro-leaks in boiler components
How to Fix / Troubleshooting
Safety: Do not repeatedly overfill the system above 2.0 bar. Allow the system to cool before working on it.
- Visual leak check: Inspect all radiators, valves, and visible pipework for signs of water. Check the pressure relief valve discharge pipe outside for drips.
- Expansion vessel test (qualified person): With the system drained or pressure at zero, measure the air charge at the expansion vessel Schrader valve. Recharge to the value specified by Alpha if low.
- PRV inspection: If the pressure relief valve has discharged water, its seat may be contaminated and it may continue to leak. Replacement is usually required.
- Monitor pressure: After topping up to 1.2–1.5 bar, note the pressure when hot. If it rises above 3 bar, the expansion vessel is likely faulty.
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Repair Difficulty
Hard
4/5
Required Part
Expansion Vessel
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