Worcester Bosch
System Water Loss / Pressure Loss
Boiler pressure keeps dropping to zero over hours or days, requiring frequent top-ups.
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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 on radiator or pipework, Leaking pressure relief valve, Internal leak in boiler (e.g. plate heat exchanger), Faulty expansion vessel
How to Fix / Troubleshooting
Safety first: Do not over-pressurise above 2.0 bar. Repeated topping up can damage the boiler.
- Visual leak check: Inspect all visible radiators, valves, and joints for signs of water or staining.
- Check PRV discharge pipe: Look outside where the copper pressure relief pipe terminates; if it drips when the boiler heats, the PRV may be passing.
- Monitor pressure: Note the pressure cold and when hot. If it rises above 2.5–3.0 bar then drops, the expansion vessel may be flat.
- Engineer tasks: An engineer should test and recharge or replace the expansion vessel, replace a leaking PRV, and locate/repair any hidden leaks.
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Repair Difficulty
Hard
4/5
Required Part
Expansion Vessel
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