we did it for a dog we had who was susceptible to kidney stones, but generally i give my rats tap water. like forensic says, if you won't drink it yourself, then your animals shouldn't either. when i decide to give them filtered water i just give it from that water dispenser on the fridge.
I currently use tap water but I'm moving soon, and i've thought about switching them to brita. Their cage will be in the living room right next to the kitchen, so I'll probably just end up grabbing the brita instead-a-ta tap!
no matter what you give to your ratties no need to feel weird about it!
My sister gives her cat super-ultra, uber-powered, mega-healthy, dome-lickin kinda thing! SHE doesn't have a system that sophisticated for HERSELF lol!!!!