Abstract: An easily sterilizable, low profile loading and unloading valve for mounting at the bottom of a tank includes a flange which is mounted adjacent to an opening in the bottom of the tank. A chamber extends through the flange, and a valve plug is mounted to one of the surfaces of the flange and extends into the tank opening. The valve plug normally closes the chamber in the flange, but is moveable to a position in which the chamber is opened to the tank. A cap is mounted to the other surface of the flange and closes the chamber. This cap may, alternatively, either take the form of a closure plate which closes the chamber during transport of the tank, or an adapter assembly which is mounted to the flange and which includes a connector for a loading and unloading conduit and a threaded biasing member for biasing the valve plug from its closed to its opened position.