http://www.newsweek.com/how-make-coffee-1393533

There's a lot of choices involved when brewing coffee, starting with perhaps the most basic ingredient: Water.

"The conventional wisdom is, if the water is good enough to drink on its own, it's good to use for coffee," David Castillo, manager of the training program at Joe and a finalist in the 2018 United States Barista Championship, tells Newsweek. "The only water you shouldn't use is distilled, because water should have a certain mineral content which helps the coffee extract. Distilled water, which pretty much has everything removed, won't extract properly and won't taste very good."