I think it depends on the water content and/or chemicals in the water supply where you live. These two threads may have some helpful information for you: Cats Drinking Tap Water Tap water
Hi. As neely
said, it depends somewhat on the water quality/chemical content in your area. All of my cats have always had tap water and as far as I know there have not been any issues with any of them related to that. If you are concerned about your water, read up on what is supposed to be accomplished with tap water/Brita filters and see if that would quell your worries.
I've been told tap water is not good for crf cats and they should have distilled or filtered water. But municipal water is fine for the majority of cats.
Well water is a different story though, some has high levels of metals and minerals which may make it unappealing for some cats.