The Worcester Bosch membrane kit is based around the diverter valve section. The diverter valve is a mechanism that only appears in combi boilers. It allows the hot water to be sent to the heating system (radiators) or to the domestic hot water system (taps). This is what separates a normal boiler from a combi boiler due to the fact that the boiler can provide hot water and heating without the need for a cylinder.

Brand Name	Worcester Bosch