D.015 High

Vaillant D.015 Fault Code

Also written as D015 — same fault.

The Vaillant D.015 fault code means: your boiler is reporting a communication error regarding how fast the water pump is moving inside the system, which typically means the boiler is struggling to circulate water effectively.. It appears on 7 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: Actualpumpspeed
Typical repair cost £150-350 (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.015 fault code

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

Source

Vaillant D.015 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 7 July 2026