BoilerFaultCodesAtag 108 Fault Code
The Atag 108 fault code means: your boiler has detected that the water pressure is too low to operate safely, meaning it needs more water added to the system.. It appears on 3 Atag models in our database.
Technical description: Pressure <0.5 bar — filling needed
DIY fix possible
Locate the external filling loop, which is usually a flexible silver hose with one or two small taps.Slowly open the tap(s) until you hear water flowing and the pressure gauge reaches between 1.0 and 1.5 bar.Close the tap(s) tightly and restart the boiler to clear the fault code.
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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 7 July 2026