S.17 Medium

Boiler Fault Code S.17

Also written as S17 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code S.17 appears across 3 boiler brands and 57 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected that the water is not flowing correctly through the heating system, likely because a valve is closed or there is a blockage. (As reported on Vaillant ecoTEC exclusive)

Pick your boiler brand for the S.17 fix

Glow-worm S.17 9 models Heatline S.17 8 models Vaillant S.17 40 models

Source

Information for the S.17 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 27 April 2026