Everyone in the house, including the dogs and cat, is on tap water. We live in a rural area, so our tap water is pretty clean. My mother even had it tested (a long time ago) because she did daycare for a while when I was little. I can't even imagine giving animals anything other than tap water, but then again, I've never lived in a place where we had to have town water. I guess it wouldn't cost too much to give a gerbil bottled water, but it sure would get expensive if you had larger animals. For instance, we have three dogs and a cat, so they go through about three large bowls of water every day.
I guess if I lived in an area where I had to buy water or filter it, I would do the same for my animals. It would just about kill me to spend the money, but it doesn't seem very fair to give them anything different than I would be drinking.
