Tap water is not good for brewing here in Phoenix...very hard and tastes bad. Most people here, including myself, use RO water and build it back up. I fill up 5 gallon jugs at RO water machines, which are everywhere around here. Only 35 cents per gallon. The machines show the date when the filters were most recently changed so I check that to make sure they are no more than a week old. Another source is Water & Ice stores. I use gypsum and calcium chloride to build back the mineral content...the ratio between the two depends on the beer style.