BoilerFaultCodes P0.5-0.9 High
Boiler Fault Code P0.5-0.9
Also written as P0509 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code P0.5-0.9 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 pressure in the central heating system to operate safely. (As reported on Potterton Powermax HE)
Pick your boiler brand for the P0.5-0.9 fix
Source
Information for the P0.5-0.9 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