It is safe for me to drink water from the tap, and my cat does not turn his nose up at tap water. I'm sure most cats and dogs ingest worse things when they are outside. Also, dogs and cats have been known to drink out of toilet bowls!
Even in poor water quality areas I think that boiling water and allowing it to cool would provide a safe drink for a pet. Buying bottled water sounds like a waste of money to me. No doubt some pampered pets are given nothing else, but I'm sure most pets do not notice the quality of their drinking water.
