BoilerFaultCodesBritish Gas 2.5 Fault Code
Also written as 25 — same fault.
The British Gas 2.5 fault code means: your boiler has shut down because it thinks the water leaving the unit has become too hot, which is usually a sign of a circulation blockage or a sensor error.. It appears on 1 British Gas model in our database.
Technical description: Max. CH flow temp.
DIY fix possible
Check that your radiator valves are fully open to allow water to flow.Ensure your system pressure is topped up to between 1 and 1.5 bar.Try resetting the boiler to see if the error clears once the water cools down.
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British Gas models that show the 2.5 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
British Gas 2.5 fault code information on this page is sourced and cross-checked against the official British Gas service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026