bL High

Atag bL Fault Code

Also written as BL — same fault.

The Atag bL fault code means: your boiler has detected that the water pressure is too low for it to operate safely and effectively.. It appears on 1 Atag model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Control is signalling insufficient water pressure
Typical repair cost £0-120 (including labour)

DIY fix possible

Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the valve(s) until you hear water flowing and the pressure gauge rises.Close the valves tightly once the pressure reaches between 1.0 and 1.5 bar on the display.

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Atag models that show the bL fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Atag bL 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