Abstract: A multiple change-over valve which can be set into various positions suite for the operation of a water treatment plant. A moulded synthetic resin body defines two valve units with seats for two movable assemblies controlled by cylinder-piston systems such as to assume two positions; each of the two movable assemblies comprises at one end a cavity with lateral apertures, and in an intermediate position longitudinal passages for cooperating with various passages, including transverse passages, between the two seats, and with passages for communication with the top and bottom of a resin column. A suction feeder for the regenerating solution, in the form of a venturi tube, is fixed between the water feed and the top of the column in order to operate when the column is connected to discharge.