It is a legal requirement (DOT ??) because of the rubber line and the length of the line pressure etc.
I had problems with mine, and it turned out to be the check valve on the passenger side main regulator. Hose comes across and goes into a check valve. you can remove check valve, just have to turn off both bottles if you remove the driver side bottle.
-2017 Ram Cummins, Aisin DRW 3.73, 4x4
-2015 Wildcat 317RL
-B&W Companion , MorRyde pinbox