D.10 High

Vaillant 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 28 Vaillant models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

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.

Typical repair cost £220-£450 (including labour)

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.10 fault code

Click a model for the full fault code list and model-specific repair notes.

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026