A ceramic disc diverter valve for use with a water treatment device. The diverter includes a movable disc sandwiched between two stationary discs. The movable disc is rotated between three different positions to deliver a stream of untreated water, a spray of untreated water or a flow of treated water. When delivering treated water, the diverter directs the flow of water out of a secondary outlet to a water treatment device. The treated water is returned to the diverter through a secondary inlet and is discharged from the diverter through a treated water outlet. When delivering untreated water, both the secondary inlet and the secondary outlet are sealed by the ceramic discs. The movable disc preferably includes an integral handle that protrudes from the housing.