BoilerFaultCodesBaxi 05 Fault Code
The Baxi 05 fault code means: your boiler has detected that the water pressure level inside the heating system has dropped too low for it to operate safely.. It appears on 3 Baxi models in our database.
Technical description: alternates with System Water Pressure
DIY fix possible
Locate the external filling loop, which is a silver braided hose connected between two valves near your boiler.Open the valves slowly to allow water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Fully close both valves and check the pressure gauge to ensure it stays stable.
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Baxi models that show the 05 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Baxi 05 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026