Abstract: An air and gas vessel (1) having a downward opening is mounted within a tank (10, 20) for transport of liquid, e.g., oil. From the top side of the vessel runs a conduit (2) toward the inlet of the bridging hose (5) to the next tank. The conduit (2) may be closed by means of a cock (3). When the tank is filled with liquid from level A with the cock (3) closed, a volume will be stored in the vessel (1) when the tank is filled to level B. In order to drain the bridging hose (5), the cock (3) is opened. The confined air/gas volume will use up into the bridging hose (5) and the liquid volume will run back into the tank. The tanks may then be closed by means of the cocks (4) prior to starting the transport.