How much does it cost to fix Saunier Duval error code 1 8?

Typical repair cost for the Saunier Duval 1 8 fault is £150-250 including labour.

1 8 High

Saunier Duval 1 8 Fault Code

Q: What does the Saunier Duval 1 8 fault code mean?

Your boiler has detected that the water inside the unit is dangerously overheated, so it has safely shut itself down to prevent damage.

Also written as 18 — same fault.

The Saunier Duval 1 8 fault code means: your boiler has detected that the water inside the unit is dangerously overheated, so it has safely shut itself down to prevent damage.. It appears on 2 Saunier Duval models in our database.

Technical description: The heating flow thermistor is detecting a temperature in excess of 100°C.

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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Saunier Duval models that show the 1 8 fault code

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

Source

Saunier Duval 1 8 fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.

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