F35 High
Your boiler has detected that the water pressure is either too low or the sensor that measures it is not working correctly.
Technical description: Incorrect system water pressure – possible cause is pressure too low or sensor damaged – the system may need filling or check the sensor
Typical repair cost: £80-180 (including labour)
DIY fix possible
Check the pressure gauge on the front of the boiler; it should ideally be between 1 and 1.5 bar.Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Slowly open the valves until you hear water entering and the pressure gauge rises to 1.2 bar, then close the valves tightly.Reset the boiler to clear the fault code.
Protect yourself from future repair bills
A boiler cover plan would cover faults like F35 — no call-out fees, no surprises.
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Parts commonly replaced
- Water pressure sensor
- Filling loop valve
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