Boiler Fault Code F.23

Also written as F23 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code F.23 appears across 2 boiler brands and 59 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 circulate water properly, often because the system pressure is too low or there is trapped air preventing the heat from moving away from the boiler. (As reported on Vaillant ecoMAX 613)