The Potterton diverter valve is a device that only appears in combi boilers. It allows the hot water to be sent to the central heating (radiators) or to the hot water system (taps). This is what separates a normal boiler from a combi boiler due to the fact that boilers are able to provide heating and hot water without requiring a cylinder.
Fits a number of Potterton boilers
Technical specification
TypeDiverter ValveMaterialMetalColourBrassManufacturer Model No10/20351Brand NamePotterton