Abstract: A water purifier including a body section, a cartridge section for purifying water, and a spool section. A horizontal water passage which is provided in the main body constituting the body section has a large-diameter portion opened to the outside of the main body and a small-diameter portion connected to the cartridge section. A vertical water passage is provided in the main body in communication with the large-diameter portion and therein a spool sleeve is disposed. A spool body including an "O" ring is provided such as to change the direction of flow of the horizontal water passage by selectively coming into contact with the continuous portion leading from the large-diameter portion to the small-diameter portion and the spool sleeve without making any contact with the edges which communicate the vertical water passage with the large-diameter portion, thereby avoiding the impairment of the "O" ring and lengthening the life of the water purifier.