S.22 Low

Glow-worm S.22 Fault Code

Also written as S22 — same fault.

The Glow-worm S.22 fault code means: your boiler is performing a routine self-check of the internal pump before it starts the main heating process.. It appears on 9 Glow-worm models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Pump pre run

What causes the Glow-worm S.22 fault?

This status occurs as part of the boiler's normal start-up sequence to ensure the internal pump is moving water correctly before the burner ignites. It is not a breakdown, but rather a safety and efficiency check to prevent the heat exchanger from overheating. If this code stays on the screen for a long time, it may suggest that the pump is struggling to reach its required speed or there is air trapped in the system.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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Glow-worm models that show the S.22 fault code

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

Source

Glow-worm S.22 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 27 April 2026