BoilerFaultCodesSaunier Duval 0.5bar Fault Code
Also written as 05BAR — same fault.
The Saunier Duval 0.5bar fault code means: your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.. It appears on 4 Saunier Duval models in our database.
Technical description: Lack of water fault (<0.5b)
DIY fix possible
Locate the external filling loop, which is usually a flexible silver hose connected to two valves beneath the boiler.Open both valves slowly to allow cold mains water to enter the system until the pressure gauge on the front reads between 1.0 and 1.5 bar.Ensure both valves are fully closed tightly and check the boiler display to see if the error has cleared.
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Saunier Duval models that show the 0.5bar fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Saunier Duval 0.5bar fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026