Worcester Bosch Expansion Vessel 10 Litre 8737709142

The Worcester Bosch 8737709142 is a 10 litre expansion vessel used in Worcester Bosch domestic heating appliances. It sits on the heating circuit and absorbs the volume increase as the system water heats and expands, holding the pressure steady instead of letting it climb. Without a working vessel the circuit pressure swings widely, the pressure relief valve can discharge, and the boiler may lock out on low pressure.

This is a Worcester Bosch spare supplied under part number 8737709142, with alternative number 2249120 also used to identify it.

• System pressure rises sharply when the boiler heats up and falls again once it cools.
• The pressure relief valve discharges water, often seen as a drip from the discharge pipe outside.
• The boiler loses pressure repeatedly and needs frequent topping up.
• Water is heard sloshing or knocking inside the vessel when the case is tapped.
• The vessel holds no charge when the Schrader valve is checked with a pressure gauge.

• Check the GC number and serial plate on the appliance against the compatibility list to confirm the correct vessel for your model.
• Confirm the part number on the existing vessel or in the manufacturer's literature, as 2249120 is also used for this component.
• Check whether a sealing washer or connection gasket is required for the vessel union and order it separately if needed.
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.