F26 High
Your boiler has detected that the water is getting hot too quickly or the temperature difference between pipes is too wide, often caused by poor water flow.
Technical description: Maximum delta temperature
Typical repair cost: £120-350 (including labour)
DIY fix possible
Check that all radiator valves and isolation valves are fully openEnsure there is enough water pressure by checking the boiler gauge (target 1.5 bar)Bleed all radiators to remove trapped air that might be blocking flowReset the boiler to see if the fault clears
Protect yourself from future repair bills
A boiler cover plan would cover faults like F26 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation pump
- Main heat exchanger (flushing)
- Flow/Return thermistor NTC
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