Medium
FILL (flashing) on Atag Q 25S

Your boiler has lost water pressure and needs you to top it up to restore full heating and hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Water pressure is too low (<1.0 bar), flashing FILL will alternate with indication of water pressure, boiler power of 50% is possible. The installation needs to be topped up.

From this model's manual
Verified against the Atag Boiler Q 38s installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Locate the external filling loop or internal filling key attached to your boiler pipework.Open the valve(s) slowly to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve(s) tightly and ensure the fault code has cleared.

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