Chaffoteaux Diverter Valve (Page 5)
The diverter valve is directional water device that only appears in combi boilers. It allows the hot water to be guided to the central heating (radiators, etc.) or to the domestic hot water system (taps, etc.). This feature is what seperates a normal boiler from a combi boiler due to the fact the boiler can provide hot water and heating without the need for a cylinder.