A flow diverter is a water system valve that lets you deviate water flow in several outlets. The diverter is essential for bathtub and shower taps if there are two outlets: spout and handshower for the bathtub and handshower and rainshower for the shower. In case you have a third additional outlet you need to install a three way diverter and a cut-off cock. For more complex shower sets, with lateral rainshowers added to the handshower and rainshower, you can have up to six way diverter (1 inlet and 5 outlets). Manual diverters are the one with a lever or a knob while automatic ones have a button for the flow deviation. It is often built in the bathtub or shower set but it has to match the style of the taps and spouts chosen.