Abstract: A valve assembly has a valve housing having hot- and cold-water inlet ports and a mixed-water outlet port and a valve disk fixed in the housing, centered on an axis, and having a face formed with respective arcuate hot- and cold-water grooves offset diametrically opposite to each other relative to the axis, each aligned with and receiving flow from the respective inlet port, and having centers of curvature at the axis, a is also formed with a central throughgoing outlet opening. A movable valve disk sitting flat on the face of the fixed valve disk is formed with a pair of axially throughgoing arcuate openings offset diametrically opposite to each other and having centers of curvature at the axis and is also formed with a central throughgoing outlet opening aligned with the outlet opening of the fixed disk. The openings and grooves each have an arc length of less than 90.degree..