F25 High
Your boiler has detected that the water temperature is rising too quickly, which usually means the water isn't flowing through the system properly.
Technical description: Maximum temperature rise slope
Typical repair cost: £120-£350 (including labour)
DIY fix possible
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 barBleed all radiators to remove trapped air from the system
Protect yourself from future repair bills
A boiler cover plan would cover faults like F25 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation pump
- Main heat exchanger
- Temperature sensors (NTC thermistors)
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