If I'm out of bottled water in the fridge I panic. I refuse to drink the tap water. A case of water is cheap anyway providing you buy the store brand. I've heard that they put in tap water in bottled water but I look on the side of it and it will mention it's been filtered in some better process and gone through reverse osmosis and I don't think municipal water does that. And I'm suspicious of the fluoride they add in the municipal water.
Sure, the water in the these bottles may start out from some municipal tap but before it's bottled it gets treated more rigorously.