Sime Rectangular Expansion Vessel 8 Litre 5183710

The Sime 5183710 is a rectangular expansion vessel with an 8 litre capacity and a 3/8 inch male connection. It is fitted to Sime gas boilers, where it absorbs the expansion of water as the system heats up and limits pressure swings across the sealed heating circuit. The vessel is a serviceable component of the boiler's hydraulic assembly.

• Boiler pressure rises sharply while the heating is running and drops again once it cools.
• Water discharges from the pressure relief valve during heating cycles.
• The pressure gauge reads high with the system cold, or the boiler locks out on pressure faults.
• Water or air escapes from the vessel's air valve when it is depressed.
• The vessel feels heavy or waterlogged when tapped, indicating a failed internal diaphragm.

• Confirm the boiler model against the manufacturer's parts list.
• Check that the connection is 3/8 inch male and that the mounting position suits a rectangular vessel.
• Verify the 8 litre capacity matches the requirement for the appliance.
• Inspect related components, such as the pressure relief valve and system pressure, before fitting.