BoilerFaultCodesVaillant D.22 Fault Code
Also written as D22 — same fault.
The Vaillant D.22 fault code means: your boiler is currently trying to communicate with your hot water tank, but it is not receiving the signal it expects from the connection.. It appears on 24 Vaillant models in our database.
Technical description: Externalcylindercharging,terminalC1-C2
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Vaillant models that show the D.22 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoMAX
- ecoMAX 613
- ecoMAX 618
- ecoMAX 622
- ecoMAX 635
- ecoMAX 824/2 E
- ecoMAX 828/2 E
- ecoMAX 835 E
- Ecomax Condensing 600/800 series
- ecoTEC plus VU GB 656/4-5 A Repair: £120-250
- ecoTEC sustain
- Home Combi 25
- Home Combi 30
- Home Combi 35
- Turbomax 824/828
- Turbomax Plus
- Turbomax Plus 824/828E
- Turbomax Plus 828 Repair: £0-120
- Turbomax Plus 828 E
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH
Source
Vaillant D.22 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 835 manual (PDF)
- Vaillant Ecomax Condensing 600/800 series manual (PDF)
- Vaillant ecoMAX 835 E manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026