BoilerFaultCodesAtag 108 Fault Code
The Atag 108 fault code means: your boiler has stopped working because the water pressure is too low and the system needs to be topped up.. It appears on 2 Atag models in our database.
Technical description: Pressure <0.5 bar — filling needed
DIY fix possible
Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Open the one or two taps/levers on the loop slowly until you hear water entering.Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.
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Atag models that show the 108 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Atag 108 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026