F.81 High

Vaillant F.81 Fault Code

Also written as F81 — same fault.

The Vaillant F.81 fault code means: your boiler is struggling to pump hot water into your storage tank, which means you may have no hot water or a significantly delayed supply.. It appears on 6 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: actoSTOR charging pump defective; only in combination with F.91: Cylinder is not fully charged after specified time
Typical repair cost £250-450 (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 F.81 fault code

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

Source

Vaillant F.81 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 31 August 2026