BoilerFaultCodesAtag 1P4 Fault Code
The Atag 1P4 fault code means: your boiler has detected that the water pressure is getting too low and needs a top-up to prevent it from shutting down.. It appears on 18 Atag models in our database.
Technical description: Pressure 0.5–0.8 bar — filling needed
DIY fix possible
Locate the blue-handled filling link underneath the boiler.Slowly pull the lever down to allow water into the system.Watch the pressure gauge and close the lever when it reaches between 1.2 and 1.5 bar.
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Atag models that show the 1P4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Atag 1P4 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