BoilerFaultCodesAriston 1 09 Fault Code
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 10 Ariston models in our database.
Technical description: System pressure > 3 bar
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.
- Ariston Challenger 80E manual (PDF)
- Ariston Clas ONE System manual (PDF)
- Ariston E-System ONE manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026