BoilerFaultCodes 12.5 High
Boiler Fault Code 12.5
Also written as 125 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 12.5 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is displaying a technical pressure setting that is not meant for user adjustment and indicates that the burner is not operating within its required parameters. (As reported on Glow-worm Betacom C)
Pick your boiler brand for the 12.5 fix
Source
Information for the 12.5 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 7 July 2026