D.22 Low

Boiler Fault Code D.22

Also written as D22 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code D.22 appears across 3 boiler brands and 52 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)

Pick your boiler brand for the D.22 fix

Glow-worm D.22 8 models Heatline D.22 7 models Vaillant D.22 37 models

Source

Information for the D.22 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 7 July 2026