Boiler Fault Code 1 3

Also written as 13 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code 1 3 appears across 2 boiler brands and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is detecting high levels of limescale build-up in your water system, which can reduce efficiency and lead to blockages over time. (As reported on Grant Vortex Blue)