I have a water softener. That's what my cats drink (it's what we drink).
There has never been issues, my house is 27 yrs old and the cats who have always lived there since my youth (I bought my parents house so basically I've had the house for 27 yrs... in a way) have never had health problems.
The only thing I've noticed is, 4 of my 6 cats are kinda fat. My mom's cats also were fat. Mom however does not have a water softener at her new condo; she's been there for 1.5 yrs, and well, her cats are still fatter than ever (and her doggie is also plump!) so I don't think the water affects them.
I an the cats drink Bottled water.........
When we lived in gloucester the water was always brown and gross....pipes were always braking...So now we all drink spring water
I am not sure where Buddy drinks from, but I catch KC in the tub all the time drinking from the dripping faucet. Elmer taught her that one when she was a rescued kitten.
On one of the email message board I am on a lady gives her cat water made pure by reverse osmosis! She has some kind of filter under her kitchen sink and the cats water bowls are filled from it.
Right now I give my cats water from those water machines in stores. I get about 14 or more filled at one time and use a gallon every 24 hours as I have 4 cats! When (when that will be I have NO idea)<sigh> I get some money I want to get a filter under my sink as even the low price of .25 a gallon DOES add up!
Mine drinks whatever he can get ahold of with the exception of his water bowl. He even tried to drink my hot chocolate this morning. Silly boy! Mostly though we give him filtered water. He will drink from the sink sometimes if the water is running.