BoilerFaultCodesVaillant S.27 Fault Code
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 46 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.
- Atmomax
- ecoFIT Pure 412
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 435
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoMAX
- ecoMAX 613
- ecoMAX 618
- ecoMAX 622
- ecoMAX 635
- ecoMAX 824E
- ecoMAX 828E
- Ecomax Condensing 600/800 series
- ecoMAX System 612
- ecoTEC
- ecoTEC 65kW
- ecoTEC exclusive
- ecoTEC Plus 610
- ecoTEC Plus 615
- ecoTEC Plus 620
- ecoTEC Plus 625
- ecoTEC Plus 630
- ecoTEC Plus 635
- ecoTEC Plus 826
- ecoTEC Plus 840
- ecoTEC Plus 938
- ecoTEC plus aquaPLUS Repair: £0-120
- ecoTEC Pro
- ecoTEC Pro / ecoTEC Plus
- ecoTEC Pro 24
- ecoTEC Pro 28
- ecoTEC Pro 30
- ecoTEC sustain
- Home Combi
- Home System
- Thermocompact
- Turbomax 824/828
- Turbomax Plus
- Turbomax Plus 824/828E
- Turbomax Plus 828
- Turbomax Plus 828 E
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH
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.
- Vaillant ecoFIT Pure 412 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoMAX manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026