The Potterton diverter valve is a mechanism that only appears in combi boilers. It allows the hot water to be redirected to the central heating (radiators) or to the domestic hot water system (taps). This is what makes a combi boiler so popular due to the fact that a combi boiler wouldn't require a cylinder to deliver heating and hot water.
Fits multiple appliances
Technical specification
Waist Sizeac17cf12guTypeDiverter ValveToilet Cistern CapacityFTW--Supplier Part Number26009160Brand NamePotterton