Tap water isn't drinkable in Arizona. It tastes noticeably bad, and if I don't let it run for a few days, then when I first turn on the faucet brown sludge will come out for 5-10 seconds first before the water starts running clear again.
So I always just get bottled water. While I'm out, if I'm camping near Phoenix/Prescott area I'll bring some filtered water with me, and if I'm in Flagstaff I'll just drink from the rivers/streams.