How much does it cost to fix Vaillant error code S.27?

Cost varies. Contact a Gas Safe registered engineer for a quote.

S.27 Low

Vaillant S.27 Fault Code

Q: What does the Vaillant S.27 fault code mean?

Your boiler is briefly running its internal pump to circulate water and manage heat after it has been turned off, which is a normal operating state rather than a breakdown.

Also written as S27 — same fault.

The Vaillant S.27 fault code means: your boiler is briefly running its internal pump to circulate water and manage heat after it has been turned off, which is a normal operating state rather than a breakdown.. It appears on 41 Vaillant models in our database.

Technical description: Pump over run (warm start)

What causes the Vaillant S.27 fault?

This status occurs when the boiler has finished heating your home or water and needs to dissipate the remaining heat from the internal heat exchanger. The pump continues to run for a short period to circulate water and prevent the internal components from getting too hot while the burner is off. It is a protective feature designed to prolong the life of your boiler and is not a sign of a mechanical failure.

DIY fix possible

Check if your heating or hot water is still working as normalWait a few minutes for the status code to change automaticallyEnsure your radiator valves are open to help heat dissipate

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Vaillant models that show the S.27 fault code

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

Source

Vaillant S.27 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026