Worcester Bosch diverter valve is a device that only appears in combi boilers. It allows the hot water to be directed to the central heating (radiators, etc.) or to the hot water system (taps, etc.). This feature is what separates a normal boiler from a combi boiler due to the boiler's being able to provide heating and hot water without requiring a cylinder.
Fits a number of Worcester appliances
Technical specification
TypeDiverter ValveSupplier Part Number87161127860Brand NameWorcester Bosch