BoilerFaultCodesVaillant S.22 Fault Code
Also written as S22 — same fault.
The Vaillant S.22 fault code means: your boiler is briefly preparing itself to provide hot water and this status code is a normal part of its operation.. It appears on 14 Vaillant models in our database.
Technical description: DHW mode: Pump pre-run. The pump prerun for domestic hot water mode is activated.
What causes the Vaillant S.22 fault?
This status code appears when the boiler detects a demand for hot water and is preparing the system to deliver it. It occurs because the internal pump needs to run for a few seconds to circulate water through the heat exchanger before the burner ignites. It is a sign that the boiler is functioning exactly as intended and is not an indication of a breakdown.
DIY fix possible
No action is required as this is a normal status message.Wait a few moments for the boiler to finish its pre-run cycle.Check if your hot water taps are working as intended.
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Vaillant models that show the S.22 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant S.22 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
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Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026