Might pick up a used Python water changer today—only gently used. Poster says no copper was run through it in water changes. Is this piece of used equipment safe? Would it be fine with a vinegar soak?
Fine and dandy. Any copper run through it wouldn't be measurable/significant. I personally clean everything used (and my old stuff) with dish soap and water and a very good rinse. Vinegar is fine for a soak as well.