I use distilled, or regular RO drinking water. I never use tap water. I do this not so much because my tap is bad, its pretty clean at only 100-200 p, but I use glass enclosures and I hate water stains. If your water looks milky, aside from checking its contents, I would not use it. I remember when my brother moved to Fresno, he found the tap water had traces of arsenic and mercury. He spent 6k on an RO system.