Floor cleaning machine with a machine frame, with a chassis which is attached to the machine frame for moving the floor cleaning machine over a floor surface to be cleaned, with a container which is fastened to the machine frame and in which a fresh water chamber and a wastewater chamber are provided, means being provided to convey liquid from the fresh water chamber onto the floor surface to be cleaned, and means being provided to convey liquid from the floor surface to be cleaned into the wastewater chamber, and the wastewater chamber having means to discharge liquid from the wastewater chamber, with a flexible diaphragm, the diaphragm being fastened to the wall of the container at at least one fastening point which is spaced apart in the vertical direction from a bottom surface of the container, with the result that the fresh water chamber and the wastewater chamber are separated from one another by way of the diaphragm between the bottom surface of the container and a horizontal plane which runs through the fastening point, either the fresh water chamber surrounding the wastewater chamber or the wastewater chamber surrounding the fresh water chamber, the diaphragm being fastened to the wall, preferably to the bottom surface, of the container, below the fastening point as viewed in the vertical direction in such a way that an opening in the diaphragm and an opening in the wall of the container coincide, with the result that liquid can flow through the opening in the diaphragm and through the opening in the wall of the container, characterized in that a filling tube is provided in the wastewater chamber, the filling tube having an inlet opening and an outlet opening which leads to the wastewater chamber, the outlet opening of the filling tube being arranged below the inlet opening of the filling tube in the vertical direction, and means being provided to convey liquid from the floor surface to be cleaned into the inlet opening. with a chassis which is attached to the machine frame for moving the floor cleaning machine over a floor surface to be cleaned, with a container which is fastened to the machine frame and in which a fresh water chamber and a wastewater chamber are provided, means being provided to convey liquid from the fresh water chamber onto the floor surface to be cleaned, and means being provided to convey liquid from the floor surface to be cleaned into the wastewater chamber, and the wastewater chamber having means to discharge liquid from the wastewater chamber, with a flexible diaphragm, the diaphragm being fastened to the wall of the container at at least one fastening point which is spaced apart in the vertical direction from a bottom surface of the container, with the result that the fresh water chamber and the wastewater chamber are separated from one another by way of the diaphragm between the bottom surface of the container and a horizontal plane which runs through the fastening point, either the fresh water chamber surrounding the wastewater chamber or the wastewater chamber surrounding the fresh water chamber, the diaphragm being fastened to the wall, preferably to the bottom surface, of the container, below the fastening point as viewed in the vertical direction in such a way that an opening in the diaphragm and an opening in the wall of the container coincide, with the result that liquid can flow through the opening in the diaphragm and through the opening in the wall of the container, characterized in that a filling tube is provided in the wastewater chamber, the filling tube having an inlet opening and an outlet opening which leads to the wastewater chamber, the outlet opening of the filling tube being arranged below the inlet opening of the filling tube in the vertical direction, and means being provided to convey liquid from the floor surface to be cleaned into the inlet opening.