Boiler Fault Code Flow Switch

Also written as FLOWSWITCH — same fault.

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

Fault code Flow Switch appears across 1 boiler brand and 1 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 there is not enough water flowing through it, so it has safely shut itself down to prevent damage to its internal components. (As reported on Potterton Promax FSB 30HE)