Ariston Expansion Vessel 65103499

The Ariston 65103499 is an expansion vessel intended for use in the Ariston ACO 35 HP MFFI UK appliance. It absorbs the expansion of water as the system heats, limiting pressure rise within the sealed heating circuit. The vessel is a serviceable component and is replaced when the internal diaphragm or charge can no longer hold system pressure.

• System pressure rises sharply when the appliance heats up and falls again once it cools.
• The pressure relief valve discharges water during normal heating cycles.
• Water is present at the vessel's air valve when the valve core is depressed.
• The boiler loses pressure repeatedly and requires frequent topping up.
• The pressure gauge reads high on start-up even with a cold system.

• Confirm the appliance model and GC number against the manufacturer's parts list.
• Check the part number on the existing vessel or in the appliance documentation matches 65103499.
• Verify that the vessel is the failed component and not the pressure relief valve, filling loop or system charge.
• Confirm the vessel's mounting position and connections on your appliance before ordering.