BoilerFaultCodes 1 P1 High
Boiler Fault Code 1 P1
Also written as 1P1 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 1 P1 appears across 1 boiler brand and 14 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 water is not moving around your heating system fast enough, triggering a safety shut-off to prevent overheating. (As reported on Ariston Clas One)
Pick your boiler brand for the 1 P1 fix
Source
Information for the 1 P1 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