IMHO
I'd still try it on an old spare part (get at junk yard). (bonus, you get to perfect your other techniques on this)
If IRCC (and i may be wrong) castile soap contians oils. So waxing may be worthless.
Metro Vac = GREAT CHOICE
JMO, but acquiring a junkyard part for this experiment is overkill. Countless people use water from water softeners w/o reporting ill effects. There seems to be potential for undissolved salts and no one bats an eye.
Yes, castile soaps contain vegetable oils (olive oil is one choice) rather than animal fats (tallow). For personal hygiene I prefer them. Haven't ever considered using them for car wash, but I don't get how waxing would be worthless? I've waxed following a wash with a wash-n-wax type product w/o issues.
