How much does it cost to fix Atag error code C15?

Typical repair cost for the Atag C15 fault is £150-250 including labour.

C15 High

Atag C15 Fault Code

Q: What does the Atag C15 fault code mean?

Your boiler is struggling to detect the movement of water inside the system, which is preventing it from heating your radiators or hot water properly.

The Atag C15 fault code means: your boiler is struggling to detect the movement of water inside the system, which is preventing it from heating your radiators or hot water properly.. It appears on 1 Atag model in our database.

Technical description: Flow sensor fault

Typical repair cost £150-250 (including labour)

Engineer required

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

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Atag models that show the C15 fault code

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

Premier Repair: £150-250

Source

Atag C15 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.

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