F75 High

Vaillant F75 Fault Code

The Vaillant F75 fault code means: your boiler is struggling to detect water moving through the system properly, which is preventing it from safely starting up.. It appears on 1 Vaillant model 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: Flow rate achieved is insufficient during the purge programme (in conjunction with diagnostic code D.149=8).
Typical repair cost £180-350 (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 F75 fault code

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

Source

Vaillant F75 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