Digital Water purity tester.. this is cool!!

RO is perfectly fine to get out bacteria...to a certain extent. IF the RO filters get colonized on the "down hill side" your screwed. With RO, as long as there isnt a hole in the filter membrane only water passes. Bleach(chlorine) may have been used to help with storage time and any bacteria that got past the RO membrane.

hammer...potablity as far as solids( too hard is not really drinkable) yes but not microbiological. TDS is minerals and ions, not critters. They arent dissolved.