So "spotless water" then?.........Is that what I know as DI (de-ironised) or DM (de-mineralised) water?
If so, I`ve successfully been using my, sorry, `DI Water`, hospital quality filter plant, that I made about 3 years ago with superb results! I can honestly say that I have not used any `car-wash` detergents, foams, drying-aids or ANY polishes etc in that time. Just, when VERY mucky, spray over with a mild TFR, jet off with a good pressure washer than simply rinse over the whole car, at mains pressure, with my DI water hose/spray. Dont really need to towel it off as it dries spot-free on it own, but, there`s something about pulling a clean/dry towel-sheet over this curvy car, very satisfying!
Couple of snaps of my plant/install for reference (all fed directly from the mains water and so `on-tap` and `on-demand`)