I have a 60 gal RDS gravity feed. The fuel goes from the aux. tank to the main tank. If I want to shut it off there is a value in the line. No problems I have been using this tank for 4 years in 2 different trucks. When my truck fuel gauge moves I know the tank is empty. There also is a gauge on the tank. I use a BAK FLIP cover and there is no issues. I installed it myself fairly easy if you know your way around a tool box. The whole thing cost around $600.00. I cannot tell you how much money I have saved by being able to buy fuel at the lowest price rather then along the interstate. We fulltime.