BoilerFaultCodesAtag A6 Fault Code
The Atag A6 fault code means: your boiler has detected that the water pressure inside the system is too low for it to operate safely and efficiently.. It appears on 2 Atag models in our database.
Technical description: Water pressure
DIY fix possible
Locate the external filling loop, which is a flexible silver hose connected to the underside of the boiler.Open the small valve or tap attached to the loop to allow mains water to enter the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (usually 1.0 to 1.5 bar).Close the valve firmly and ensure the flexible hose is disconnected if required.
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Gas Safe Register →Atag models that show the A6 fault code
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Source
Atag A6 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 27 April 2026