A mixing valve has a housing holding a fixed valve plate a flat outer surface generally centered on and perpendicular to an axis and formed offset from the axis with a pair of angularly offset and axially throughgoing inlet ports and offset therefrom with a pair of axially throughgoing outlet ports. Hot and cold water is supplied under pressure to the inlet ports and passages in the housing connect the outlet ports to respective users, e.g. a faucet and a shower. A movable valve plate in the housing has an inner surface flatly engaging the outer surface of the fixed valve plate and an opposite outer surface and is formed with an axially throughgoing inlet port alignable with the fixed-plate inlet ports and offset from the respective inlet port an axially throughgoing outlet port alignable with the fixed-plate outlet ports. A cover element fixed in the housing to the outer surface of the movable plate forms a fluid-flow passage at the outer surface between the movable-plate inlet port and the movable-plate outlet port. An actuator can shift the cover element and movable plate between a closed position with one of the movable-plate ports out of alignment with the respective fixed-plate ports and blocked by the fixed-plate outer face and two open position in each of which the movable-plate inlet port aligned with at least one of the fixed-plate inlet ports and the movable-plate outlet port aligned with a respective one of the fixed-plate outlet ports.