BoilerFaultCodesVaillant d.13 Fault Code
Also written as D13 — same fault.
The Vaillant d.13 fault code means: your boiler is struggling to communicate with an external water pump that is typically used in larger heating systems, preventing the warm water from moving around your home correctly.. It appears on 19 Vaillant models in our database.
Technical description: External circulation pump when fitted (ecoMAX 835)
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.13 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 825 Repair: £150-300
- ecoFIT Pure 830 Repair: £150-350
- ecoFIT Pure 835
- ecoMAX Repair: £150-300
- ecoMAX 613 Repair: £120-250
- ecoMAX 618 Repair: £120-250
- ecoMAX 622 Repair: £120-250
- ecoMAX 635 Repair: £150-300
- ecoMAX 824/2 E Repair: £120-250
- ecoMAX 828/2 E Repair: £120-250
- ecoMAX 835 E Repair: £120-250
- Ecomax Condensing 600/800 series Repair: £150-300
- ecoTEC plus VU GB 656/4-5 A Repair: £180-350
- ecoTEC sustain
- Home Combi 25 Repair: £150-350
- Home Combi 30 Repair: £150-350
- Home Combi 35 Repair: £150-350
Source
Vaillant d.13 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 425 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant Ecomax Condensing 600/800 series manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026