I have a Lund 50 gallon aux. gravity fed tank. I installed it about 1 year ago. I have a solenoid in line along with a switch in the cab of the truck to turn on and off (open/close). I drilled out a hole in my filler neck and welded a bung to it. Tested for leaks and attached the fuel line from the solenoid to it. From my tank to the solenoid is about 12" of line. When the solenoid is open to fill the tank it is slow but keeps up with the truck when traveling. I accidentally left my switch on (open) one day at work - oops. When I got out of work the truck was "full" to the level of the bung / incoming hose and did not fill over that. I did put a shutoff valve coming out of the tank for emergency in the event. I was concerned about that my truck, 2015 Ram would throw a code but in the 1 year of using it, nothing. Even my "distance to empty" gauge in the truck calculates as it fills going down the road. :)