Potterton Diverter Valve (Page 3)
The diverter valve is a part that only appears in combi boilers. It allows the hot water to be sent to the central heating (radiators, etc.) or to the hot water system (taps, etc.). This feature is what seperates a normal boiler from a combi boiler due to the diverter valve allowing use of hot water and heating without the need for a cylinder