I don't know whether there's anything harmful in your fountain. What do you put in it?
I do know that if your kitties like drinking running water, you should get them a pet fountain. I have the Drinkwell Platinum http://bit.ly/2Yyxw2
and love it. My Maine Coon mix Bassie used to jump in the sink begging for someone to turn on the faucet until we got her the fountain. Now all the cats are using it. Even though 2 drink from the bowl rather than the stream, they still prefer water from the fountain to that from a regular water bowl.
Hope that helps.
Miami, FL, USA