Boiler Fault Code D.22

Also written as D22 — same fault.

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

Fault code D.22 appears across 1 boiler brand and 28 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is currently preparing or delivering hot water, which is a normal operating status of the pre-heat function rather than a failure. (As reported on Vaillant Thermocompact)