Method for draining water from a tank

A draining apparatus for draining water from a tank (22), comprising a discharge device (1) immersed in the tank (22) and having drainage openings (3) which open into the tank (22), wherein a device is provided for selectively supplying compressed air into a blocking volume (24), wherein the draining apparatus is fixedly mounted in the tank (22), and wherein the discharge device is designed as a horizontally disposed drainage pipe (1) and a uniform drawing-in of the liquid into the draining apparatus is achieved by an expansion of a distance (19) of the drainage openings (3) in the flow direction in the drainage pipe (1) or by reducing widths of the drainage openings (3) in the direction of flow in the drainage pipe (1).