b25 High

Boiler Fault Code b25

Also written as B25 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code b25 appears across 4 boiler brands and 8 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected that the water is heating up too quickly, which usually means it can't circulate water through the system properly. (As reported on Vokera Pinnacle)

Pick your boiler brand for the b25 fix

Atag b25 1 model Johnson Starley b25 4 models Remeha b25 2 models Vokera b25 1 model

Source

Information for the b25 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