BoilerFaultCodes 72:1 Medium
Boiler Fault Code 72:1
Also written as 721 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 72:1 appears across 1 boiler brand and 5 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 accurately measure the temperature of the water being heated for your taps, causing it to shut down while filling your hot water cylinder. (As reported on Viessmann Vitodens 300-W)
Pick your boiler brand for the 72:1 fix
Source
Information for the 72:1 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