A water-ejection device intended to be integrated in the middle and back portion of a toilet seat of a toilet bowl and comprising a mechanism with a water-ejection nozzle comprising a self-cleaning removable telescopic ejector, the mechanism comprising: a tap; a water supply controlled by the tap, connected, through swivel fixtures, to a shell; a piston; a removable jacket mounted within the shell and distributing the pressurized water supply in two positions, a high position enabling to move the piston and a low position for the self-cleaning and the ejection; the piston being movable, in the jacket, by the pressurized water, and held in retracted position by a spring; the opening of the tap controlling: - the extension of the water outlet nozzle, and then - at the end of the movement, the spraying of water by the ejector fitting the nozzle, actuated as soon as the head of the piston has reached a position opposite the low position of the water supply, the closing of the tap simultaneously controlling the stopping of the water ejection and the retraction of the nozzle due to the action of the spring, whereby the self-cleaning of the nozzle occurs only during phases when the nozzle is being moved out or back in, the device being characterized in that a ring-shaped chamber is formed around the head of the piston, the piston head being located opposite the low position of the pressurized water supply, said ring-shaped chamber enabling the ejector to start operating while the piston is in the end position of its movement outside the jacket, said ring-shaped chamber being in the low position of the jacket, where the pressurized water is distributed to ensure the self-cleaning and the ejection. a tap; a water supply controlled by the tap, connected, through swivel fixtures, to a shell; a piston; a removable jacket mounted within the shell and distributing the pressurized water supply in two positions, a high position enabling to move the piston and a low position for the self-cleaning and the ejection; the piston being movable, in the jacket, by the pressurized water, and held in retracted position by a spring; the opening of the tap controlling: - the extension of the water outlet nozzle, and then - at the end of the movement, the spraying of water by the ejector fitting the nozzle, actuated as soon as the head of the piston has reached a position opposite the low position of the water supply, - the extension of the water outlet nozzle, and then - at the end of the movement, the spraying of water by the ejector fitting the nozzle, actuated as soon as the head of the piston has reached a position opposite the low position of the water supply, the closing of the tap simultaneously controlling the stopping of the water ejection and the retraction of the nozzle due to the action of the spring, whereby the self-cleaning of the nozzle occurs only during phases when the nozzle is being moved out or back in, the device being characterized in that a ring-shaped chamber is formed around the head of the piston, the piston head being located opposite the low position of the pressurized water supply, said ring-shaped chamber enabling the ejector to start operating while the piston is in the end position of its movement outside the jacket, said ring-shaped chamber being in the low position of the jacket, where the pressurized water is distributed to ensure the self-cleaning and the ejection.