While I'm building my new trailer setup, trying to map out the best way I want to fill my (possible) two tanks. I already have a 300 gallon leg tank along with looking at getting a 500 gallon tank. I already have my way set up I am going to fill them (top fill with an air gap), but do I want to only fill one via the hydrant and have a 2-3" line connecting the two at the bottom? Or do I want to try to rig something up to top fill both of them? I don't know if anyone has done this or you physics guys have any suggestions?