Bosch
Chronic System Pressure Loss
Furnace frequently loses pressure and needs to be topped up with water
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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
Hidden leak in pipework or radiators, Leaking pressure relief valve, Faulty expansion vessel diaphragm, Micro-leaks in heat exchanger
How to Fix / Troubleshooting
Safety: Let the system cool before inspecting for leaks.
- Visual inspection: Check all visible pipes, radiators, and the area under the furnace for signs of water.
- Relief valve: Inspect the discharge pipe from the pressure relief valve for signs of dripping. If it is wet, the valve may be leaking or system pressure too high.
- Expansion vessel: A failed vessel can cause pressure swings. Tapping it lightly—if it sounds full of water, it likely needs service.
Locating hidden leaks and servicing the expansion vessel should be done by a heating technician.
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Repair Difficulty
Medium
3/5
Required Part
Pressure Relief Valve
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