I had a long think about it last-night and I think I'm starting to get my head around it, I think I was confused since watching a video on you tube where this guys van was all kitted out and there were many gadgets and other gizmo's attached to his van. :Image1: .No problem best you just forget about another tank with tap water in it. :Image9:
If using a ro/di in a van you would just need to connect a hose pipe from an outside tap then have the ro waste pipe feed into a drain. But to be honest using a small compact ro like that will take many hours to fill a van tank. That why so many use a small ro static instead as can produce pure water while they are out working.
The idea of the two tanks was because I was thinking that the unpurified water would not be able to run through the purifying system quicker that you can use it.