Worcester Membrane 87155058250

Worcester

The Worcester Membrane (Part No. 87155058250) is a genuine OEM (Original Equipment Manufacturer) rubber component used in the hydraulic water assembly of older Worcester Bosch appliances. This flexible diaphragm is a critical part of the DHW (Domestic Hot Water) valve or diverter valve. Its primary function is to react to the change in water pressure when a hot tap is opened; the pressure differential causes the membrane to flex, which in turn pushes a pin to activate a microswitch or move a diverter valve, signaling the boiler to provide hot water.

Key Features and Specifications
High-Flexibility Elastomer: Manufactured from high-grade, durable rubber designed to withstand thousands of "flexing" cycles without tearing or losing elasticity.

Precision Profile: Features a reinforced central section to provide a stable contact point for the diverter valve pin or spindle.

Genuine Worcester Bosch Part: Ensures the correct thickness and diameter for a perfect fit, providing the exact resistance required to operate the mechanical valve correctly.

Temperature Resistant: Engineered to maintain its integrity even when exposed to high-temperature domestic hot water over long periods.

Fault Resolution: Replacing a perished or pinholed membrane is the standard fix for boilers that fail to recognize hot water demand while the central heating continues to work.

Boiler Compatibility
This membrane is found in the hydraulic assemblies of legacy and classic Worcester models, including:

Worcester 240 Combi: (RSF, BF, and OF versions).

Worcester 280 Combi.

Worcester 350 Combi.

Worcester 9.24 models.

Note: This part is specific to models with a mechanical/hydraulic diverter valve. Modern Greenstar boilers typically use an electronic flow turbine or a motorized diverter valve instead.

Technical Tip: If your hot water is intermittent or the boiler only fires when the central heating is already on, the membrane is likely stretched or has a tiny "pinhole" leak. When replacing the membrane, it is essential to clean the internal housing of the valve and apply a small amount of silicone grease to the moving spindle to ensure smooth operation.

Essential Companion Products
To perform a professional overhaul of the hydraulic valve, the following genuine Worcester parts are frequently checked alongside the membrane:

Watertight Seal: Worcester O-Ring – 87161138510

Hydraulic Gasket: Worcester Seal – 87101031910

External Weathering: Worcester Wall Seal 160mm (Black) – 87161112120

Gas-Side Maintenance: Worcester Gas Valve Gasket – 871860034A0

Hardware: Worcester Retaining Nut – 87161066830

Specialist Support and Local Collection
Is your older Worcester boiler failing to produce hot water despite no fault codes appearing? Our trade counter team can help you identify if this membrane or the diverter valve spindle is the cause of the problem.

Visit our trade counter and Bathroom Showroom at 61 Fullers Road, E18 2QB for expert technical advice and immediate access to genuine Worcester Bosch legacy spares.