This device is a round metal tube. It is located inside the tank and attached to the transfer or fill riser pipe of an underground storage tank (UST).
Drop tubes are most commonly 4” in diameter and they extend from the top of the tank to within a few inches (usually 2” - 6”) of the bottom of the tank.
They are designed to direct the flow of product being transferred to the bottom of the tank. The end of the drop tub that is located closest to the bottom of the tank is typically cut at a 45 degree angle to facilitate the flow of product away from the tube during the transfer process.
Some drop tubes have a diffuser assembled to the bottom that directs the flow of product parallel to the bottom of the tank when it exits the tube. This minimizes disturbing any particulate or liquid resting on the bottom of the tank.
All drop tubes must be constructed from materials that are compatible with the product that is stored in the tank.