A water treatment plant with a container with periodically regenerable means for water treatment, a valve system for controlling flow rates by means of a movable control element (1), a counter-element (5) arranged in stationary fashion in a housing (4), wherein the control element bears in sealing fashion against the counter-element and can be moved, relative to the counter-element, sequentially in a periodically repeating fashion into at least two operating positions (P1, P2, P3) of an operating cycle with differently configured valve functions, and a sensor (6) for determining the position of the control element relative to the counter-element, is characterized in that there is a device for reversing the direction of motion of the control element relative to the counter-element, by means of which device it is possible to reverse the direction of motion of the control element at least once per operating cycle, and in that the sensor can be used to determine a reference position (R) of the control element, wherein the reference position is offset, in each case by a portion x0, with respect to the individual operating positions. This makes possible more rapid setting of another operating position starting from a previous operating position, the current position of the control element being determined exactly and an undesired valve setting being reliably avoided.
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