S.41 Medium

Glow-worm S.41 Fault Code

Also written as S41 — same fault.

The Glow-worm S.41 fault code means: your boiler's internal water pressure is currently too high, which means the system has taken in too much water and needs to be brought back down to a safe level to operate correctly.. It appears on 19 Glow-worm models in our database.

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.

Technical description: Water pressure too high
Typical repair cost £80-150 (including labour)

DIY fix possible

Turn off the boiler and allow it to cool down completely.Locate a radiator in your home and attach a bleed key to the valve.Open the valve slightly to let a small amount of water out into a container until the pressure gauge on the boiler drops to the recommended level (usually between 1 and 1.5 bar).Close the valve and check the boiler display to see if the error has cleared.

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Glow-worm models that show the S.41 fault code

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

Source

Glow-worm S.41 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026