E05
Keston
Low Water Pressure / Water Pressure Switch Open
Boiler shows E05, no heating or hot water, display may show low pressure symbol
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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 pressure below minimum, Leak in heating circuit, Faulty pressure sensor or switch, Blocked expansion vessel connection
How to Fix / Troubleshooting
Safety: Allow the system to cool before topping up. Do not over-pressurise the boiler.
User checks:
- Check the pressure gauge on the Keston boiler fascia. If below 1.0 bar, connect the filling loop and slowly open the valves to raise pressure to 1.0–1.5 bar, then close both valves.
- Inspect visible pipework and radiators for signs of leaks (staining, drips). If a leak is found, close the filling loop and contact an engineer.
- Reset the boiler after pressure is restored.
Engineer checks:
- Check operation of the Keston water pressure sensor/switch with a multimeter or via diagnostic mode; replace if it does not respond to pressure changes.
- Test the expansion vessel pre-charge (typically around 0.8–1.0 bar) with a tyre gauge after isolating and draining pressure from the system; recharge with a pump or replace the vessel if diaphragm has failed.
- Inspect for hidden leaks around the boiler, automatic air vents, and safety valve discharge pipe.
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Repair Difficulty
Medium
3/5
Required Part
Water Pressure Sensor
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