Valve having a rotatable stopper, and water treatment plant comprising such a valve

A valve comprising:

• a valve body delimiting a cavity, the body being provided with a first orifice allowing water to enter the cavity, with a second orifice allowing water to be discharged from the cavity, and a third orifice making it possible to place the cavity and a chamber in communication;
• a stopper or plug mounted to as to be able to rotate inside the cavity, the stopper comprising a (first) recess on its outer face, this recess helping, with the body, to delimit a passageway allowing water to travel between the first and third orifices in first angular positions of the stopper, said passageway allowing water to travel between the second and third orifices in second angular positions of the stopper;
• wherein said stopper comprises a second recess, arranged along the periphery of the stopper, said second recess facing in fluidic communication the third orifice at all angular positions of said stopper, and a channel formed in the stopper and connecting the first and second recesses;
• a first sealing device arranged so as to provide a substantially watertight stopping of the first orifice by the stopper in said second angular positions of the stopper;
• and
• a second sealing device arranged so as to provide a substantially watertight stopping of the second orifice by the stopper in said first angular positions of the stopper,
• wherein the first sealing device comprising a first housing and the second sealing device comprising a second housing, said first and second housings leading into the cavity and surrounding respectively the first and second orifices, a first sealing member slidingly arranged in said first housing, and a first pressing device for pressing the first sealing member against the stopper, a second sealing member slidingly arranged in said second housing, and a second pressing device for pressing the second sealing member against the stopper,
• wherein the first and second housings are in the shape of annular slots and the first and second sealing members have an annular—or tubular—shape adapted to the shape of the portion of the stopper against which they are pressed, and
• wherein the first pressing device associated with the first sealing member surrounding the first orifice comprises at least one first connecting channel, said first connecting channel connecting in fluidic communication the non-open end of the first housing to the inner face of a first sleeve connecting the valve to a duct, while the second pressing device associated with the second sealing member surrounding the second orifice comprises at least one second connecting channel, said second connecting channel connecting in fluidic communication the non-open end of the second housing to the cavity.