Note: To fill the mouthpiece, open the cup to the stop screw (counter-clockwise) and fill completely with water. Now swivel the mouthpiece (shaft and cup should touch the worktop) and let excess water run out. While maintaining the angle, screw the cup back in clockwise.
Please note: Do not tighten the cup all the way, there should be a small gap between the rim and the cup. The water should be renewed regularly.