BoilerFaultCodesKeston 0.5 bar Fault Code
Also written as 05BAR — same fault.
The Keston 0.5 bar fault code means: your boiler has detected that the water pressure in your heating system has dropped too low to operate safely.. It appears on 1 Keston model in our database.
Technical description: CH min working pressure
DIY fix possible
Locate the external filling loop, which is a silver braided hose connecting two pipes near the boiler.Open the valves at both ends of the hose slowly to allow water to enter the system.Watch the pressure gauge on the front of the boiler until it reaches between 1.0 and 1.5 bar, then firmly close both valves.
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Keston models that show the 0.5 bar fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston 0.5 bar fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026