How much does it cost to fix Atag error code 20?

Typical repair cost for the Atag 20 fault is £120-£200 including labour.

20 High

Atag 20 Fault Code

Q: What does the Atag 20 fault code mean?

Your boiler has lost its ability to accurately measure the temperature of the water leaving the unit, usually due to a faulty sensor or a wiring issue.

The Atag 20 fault code means: your boiler has lost its ability to accurately measure the temperature of the water leaving the unit, usually due to a faulty sensor or a wiring issue.. It appears on 5 Atag models in our database.

Technical description: Flow sensor error (e.g. open, short circuit, out of range)

Typical repair cost £120-£200 (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 20 fault code

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

A200 Repair: £120-£200
E Range Repair: £250-550
Q 25CR Repair: £150-250
S 25CR Repair: £150-250
Sov. Repair: £120-220

Source

Atag 20 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