The device has a return line (22) of smaller diameter than the supply hose (2) runs at least partially inside it. One free end (25) of the return line lies inside the supply hose with a gap between it and the end (3) of the supply hose connected to the discharge component. The return line is connected to a second connection (30) by a connecting piece (29) extending outside the supply hose. The supply hose is connected by one end (5) to one arm of a connecting T-piece (8).
