How much does it cost to fix Grant error code 31?

Typical repair cost for the Grant 31 fault is £120-250 including labour.

31 High

Grant 31 Fault Code

Q: What does the Grant 31 fault code mean?

Your boiler is struggling to get enough fresh air for the combustion process to work correctly, which is often due to an issue with the external flue or ventilation path.

The Grant 31 fault code means: your boiler is struggling to get enough fresh air for the combustion process to work correctly, which is often due to an issue with the external flue or ventilation path.. It appears on 6 Grant models in our database.

Technical description: Vent A (in²)

Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Grant models that show the 31 fault code

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

Source

Grant 31 fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026