BoilerFaultCodes d18 Low
Boiler Fault Code d18
Also written as D18 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code d18 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 currently running a special testing mode used to dry out new floor screed, which is an intentional operational setting rather than a system fault. (As reported on Alpha E-Tec Plus 10 / 18)
Pick your boiler brand for the d18 fix
Source
Information for the d18 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