It's the same thing with alcohol etc. it depends on the quantity.
If you want to be sure that you use good water take aqua demin. You can also use rainwater, if you live in a rural place without industry
If your using water from your house and you can drink it then its fine for your chams...most water for the exception of distilled bottled water has some supplements in it like calcium, magnesium etc. but as long as there is not a problem with your water from the faucet you should be fine.
Like Sandra said
Be sure that your local water supplier does not use Fluoride.
That one is definitely fatal for your cham in the long run.
If the latter is the case, then I suggest to use filtered water.
Boiling water will increase the amount of fluoride since it's a mineral. I think the only things that get it out is Reverse Osmosis Filtration, Activated Alumina Defluoridation Filter, and Distillation Filtration.
Unfortunately Brita, Pur, and most other filters do not pick up the mineral fluoride.
Which leads me to this question...what about my misting system that mists 4 times a day using water known to have minute amounts of fluoride? Also in place is a drip system that constantly drips using bottled water. Is this safe? My hopes are that the chams main drinking source is the drip system.