BoilerFaultCodes F42 High
Boiler Fault Code F42
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F42 appears across 2 boiler brands and 10 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is struggling to detect the flow of water because a sensor inside the unit is providing an incorrect reading, which prevents it from safely heating your home or water. (As reported on Ferroli Optimax HE Plus)
Pick your boiler brand for the F42 fix
Source
Information for the F42 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 31 August 2026