BoilerFaultCodes F40 High
Boiler Fault Code F40
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F40 appears across 2 boiler brands and 14 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has shut down because there is too much water pressure in the system, which can put unnecessary strain on the internal seals and pipework. (As reported on Johnson Starley Comet 80)
Pick your boiler brand for the F40 fix
Source
Information for the F40 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026