Ariston 108 error code: refill request for low system pressure

What Does Error 108 Mean?

Ariston shows 108 when the heating circuit pressure has fallen below the level the boiler needs, and it is asking for a refill. The owner opens the filling taps under the boiler until the gauge reads 1.0 to 1.5 bar cold, closes them, then clears the code with the reset control. A drop again within days points at a leak. Applies to: Ariston Clas ONE, Clas System ONE, and Alteas ONE boilers showing 108 This applies to Ariston Clas and Alteas family boilers whose user documentation lists 108 as a filling request. Ariston uses separate codes for a faulty pressure transducer, so if the gauge is already in band and 108 stays, treat it as a sensor branch and call an engineer. Owner-safe checks: With the boiler cold, open both filling taps under the boiler slowly until the gauge reads 1.0 to 1.5 bar, then turn both taps fully off and press reset once. | Note whether 108 clears after the reset and whether the pressure is still in band the next morning. Qualified technician: A pressure that will not hold, 108 showing with the gauge already in band, a suspected transducer fault, or any check inside the boiler casing needs a Gas Safe registered engineer.