Pure water isn't a given.  Not even from the store. Perhaps especially not from the store. Most store water is simply run through a filter to take out chlorine and sulphur.  That is only for taste, not health. Then it's stored in plastic jugs, often left outside in the sun for weeks.

Sheryl  Crow followed Lance Armstrong around during his racing days with bottled water by the case sitting in her car in the summer sun for weeks.

For her loyalty she developed breast cancer. She is certain it was the high levels of BPA  she consumed in the water from the plastic bottles.  Of course Lance dumped her when she was sick.

I use Zero Water system to filter drinking water at home. It came with a water tester. The advertising in Amazon sold me. I bought 2. One for Russia, and one for my place in the US.  Water taste fine to me.

One caveat though, both of my pitchers leaked. So I keep an all glass bottle for drinking.