How much does it cost to fix Heatline error code F23?

Typical repair cost for the Heatline F23 fault is £150-300 including labour.

F23 High

Heatline F23 Fault Code

Q: What does the Heatline F23 fault code mean?

Your boiler has detected that the water is not circulating properly, meaning it is getting hot in one area but not moving to the rest of your system fast enough.

The Heatline F23 fault code means: your boiler has detected that the water is not circulating properly, meaning it is getting hot in one area but not moving to the rest of your system fast enough.. It appears on 8 Heatline models in our database.

Technical description: Maximum temperature difference reached between return and fl ow heating

Typical repair cost £150-300 (including labour)

Engineer required

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

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Heatline models that show the F23 fault code

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

Source

Heatline F23 fault code information on this page is sourced and cross-checked against the official Heatline service / installation manuals for each affected model.

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