BoilerFaultCodes FILL Medium
Boiler Fault Code FILL
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code FILL appears across 1 boiler brand and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has lost enough internal water pressure that it cannot operate at full capacity, so you need to top it up to restore normal heating and hot water. (As reported on Atag E22c)
Pick your boiler brand for the FILL fix
Source
Information for the FILL 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