The cover is placed in the barrels to allow wine to ferment without interference. This prevents air from getting inside. A flexible tube is wrapped around the edge of the cover. To make it absolutely leak-proof, it is blown up with a plastic barrel pump. When the desired pressure is reached, the flexible tube can be prevented from venting with the ball valve. All parts of the barrel pump in contact with media are in compliance with the guidelines of the FDA (Food and Drug Administration).