How much does it cost to fix Ariston error code 1 09?

Typical repair cost for the Ariston 1 09 fault is £90-180 including labour.

1 09 High

Ariston 1 09 Fault Code

Q: What does the Ariston 1 09 fault code mean?

Your boiler has detected that the water pressure inside your heating system is too high, which can cause internal leaks or force the safety valve to open.

Also written as 109 — same fault.

The Ariston 1 09 fault code means: your boiler has detected that the water pressure inside your heating system is too high, which can cause internal leaks or force the safety valve to open.. It appears on 8 Ariston models in our database.

Technical description: System pressure > 3 bar

Typical repair cost £90-180 (including labour)

DIY fix possible

Locate the external heating system drain valve near a low-level radiator.Place a bucket and cloth underneath, then slowly open the valve to release a small amount of water.Monitor the boiler's pressure gauge until it drops into the green zone (usually 1.5 bar) and close the valve tightly.

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Ariston models that show the 1 09 fault code

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

Source

Ariston 1 09 fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.

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