Worcester Bosch Expansion Vessel 8 Litre 87161425150

The Worcester Bosch 87161425150 is an 8 litre expansion vessel used in the Worcester 26CDi and 26CDi XTRA RSF range of gas boilers. It sits on the heating circuit and absorbs the volume increase as the system water heats and expands, holding the pressure steady and protecting the boiler and radiators from the stress of repeated expansion and contraction. The internal diaphragm separates the water side from a pre-charged air side, so the vessel maintains system pressure across the full operating temperature range.

• Boiler pressure gauge falls steadily and needs frequent topping up, with no visible leak on the system pipework or radiators.
• Water discharges from the pressure relief valve during heat-up, often leaving a trail from the discharge pipe.
• The vessel feels heavy or full of water when the system is drained, indicating a split or perished diaphragm.
• Corrosion, staining or damp patches around the vessel connection or shell.
• Boiler locks out or shuts down on low pressure shortly after the system has been filled and vented.

• Check the boiler's GC number and model plate against the compatibility list to confirm the correct vessel for your appliance.
• Confirm the part number 87161425150 or an alternative number (1018327, WB87161425150) appears on the existing component or the manufacturer's parts listing.
• Have a replacement sealing washer or connection gasket to hand if the existing one is disturbed during removal.
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.