BoilerFaultCodesVaillant D.10 Fault Code
Also written as D10 — same fault.
The Vaillant D.10 fault code means: your boiler's internal pump is having trouble circulating water through the system, which is preventing your heating from working.. It appears on 38 Vaillant models in our database.
Technical description: Status internal heating pump error
What causes the Vaillant D.10 fault?
This fault occurs when the boiler's internal pump fails to spin or move water effectively through the system. The most common reasons are a mechanical failure of the pump motor, a build-up of debris or 'sludge' blocking the internal components, or a communication issue between the pump and the main control board.
This issue is frequently seen at the start of autumn when heating systems are turned back on after being idle all summer, as pumps can seize up during long periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A cover plan would handle faults like D.10: no call-out fees, no surprise bills.
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Vaillant models that show the D.10 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £220-450
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 435
- ecoFIT Pure 825 Repair: £250-450
- ecoFIT Pure 830 Repair: £200-400
- ecoFIT Pure 835
- ecoMAX Repair: £150-350
- ecoMAX 613 Repair: £180-350
- ecoMAX 618 Repair: £150-350
- ecoMAX 622 Repair: £150-350
- ecoMAX 635 Repair: £200-450
- ecoMAX 824E Repair: £150-350
- ecoMAX 828E Repair: £180-350
- Ecomax Condensing 600/800 series Repair: £150-£350
- ecoMAX System 612 Repair: £180-350
- ecoTEC Repair: £220-£450
- ecoTEC 65kW
- ecoTEC Plus 610 Repair: £180-350
- ecoTEC Plus 615
- ecoTEC Plus 620
- ecoTEC Plus 625
- ecoTEC Plus 630
- ecoTEC Plus 635
- ecoTEC Plus 840
- ecoTEC plus aquaPLUS
- ecoTEC Pro / ecoTEC Plus Repair: £200-450
- ecoTEC sustain
- Home Combi Repair: £200-450
- Home System
- Thermocompact
- Turbomax 824/828 Repair: £150-300
- Turbomax Plus Repair: £150-350
- Turbomax Plus 824/828E
- Turbomax Plus 828 Repair: £150-350
- Turbomax Plus 828 E
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH
Source
Vaillant D.10 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 manual (PDF)
- Vaillant ecoMAX System 612 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026