Boiler Fault Code D.13

Also written as D13 — same fault.

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

Fault code D.13 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 having trouble moving hot water through the internal pipes, which usually means the circulation pump cannot start or is stuck. (As reported on Vaillant ecoTEC)