It's not smart to use lead solder in your moonshine still either. But correct distilling is still going to give the cleanest water. Reverse osmosis
is for removing organic contaminants to create drinking water from whatever; some chemicals might get thru anyway. It's a semi-permeable
membrane system, to phrase it generically. Or you could passive filter things with a portable water purifier system - still wouldn't remove
everything. A lot depends on where you live and what the tap water is like. Here we get good snowmelt from clear across the state, so the
water quality is excellent. A few miles inland they get treated river water that is essentially over-chlorinated swimming pool water with a cocktail of agricultural runoff, incl trace amts of all kinds of pesticides. Dry climates can have very hard water with quite a bit of alkali. I hesitate to say where some of our highly advertised bottled water comes from. A least one brand is bottled at a superfund site, because nobody is actually allowed to live there anymore! The spring is some distance away ... but it still makes you want to think twice!