Abstract: A water mixing valve comprising a fixed valve seat and a valve plate which is slideable over the valve seat, means providing two modes of slideable movement of the valve plate with respect to the valve seat, one being a shifting movement and the other a rotational movement, and a porting arrangement in the valve seat and a cooperating system of passages in the valve plate, permitting shifting of the valve from a full on to a full off position at any desired mixture of hot and cold water, and permitting positioning of the valve to obtain changes in temperature of the water without change in volume, and changes in volume of the water without change in temperature.