Worcester Bosch Expansion Vessel 18 Litre 87154072300

The Worcester Bosch 18 litre expansion vessel is a diaphragm-type pressure vessel used in the heating circuit of Worcester Bosch gas boilers. It absorbs the volumetric expansion of water as the system heats up, keeping system pressure stable and protecting the boiler and radiators from excessive pressure spikes. This unit is the 18 litre variant specified for the Greenstar HE Plus and ICS1 28kW appliance families.

• Boiler pressure falls repeatedly and needs frequent topping up, with no visible leak on the system pipework or radiators.
• The pressure relief valve discharges water, or the boiler locks out on low pressure shortly after firing.
• Water is heard sloshing inside the vessel when the boiler is shaken, indicating a failed diaphragm.
• The vessel body is corroded, damp or weeping at the connection, or the Schrader valve releases water rather than air when checked.
• System pressure rises sharply and rapidly as the boiler heats, then drops again once it cools.

• Confirm the appliance model and GC number against the compatibility list, as the same boiler range can use different vessel sizes.
• Check the existing vessel for its capacity marking and connection type before ordering.
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.