I hate how much water RO wastes. I can't deal with a 4:1 waste to drinking water ratio that many of the cheap systems have, since I live in an RV and that would fill up my galley tank even faster.
Discussion
It makes sense to have it delivered or to haul it yourself in thay case
There are breweries around... I might have to go knocking on doors.
4:1 makes perfect sense if treating seawater, but quite ridiculous for fresh.
Can you adjust the cut?
Not that I'm aware of, at least in the systems I've looked at.
Darn. Reading up, doesn't look practical to mod the household units as the back pressure would be too high for their feeble pumps.
Those designed for marine applications can... but yeah probably not the right technology for your RV...