Also, tap water may have the wrong pH or may have too much alkaline in some states. But stuff like this is more important to plants and fish. For my fish tanks, I use straight tap water with a dechlorinating solution because I don't want to wait. But if you want to air it out, it only takes a day. The reason chlorine is bad for fish is because of their gills. Chlorine binds with their gills and prevents the gills from obsorbing oxygen properly. You, I, and geckos don't have gills.
Even though the quality varies depending on where you live, tap water is designed to be safe to drink. I happen to live near Boston, which has above than average in terms of quality. I still use Brita filter though. I find that the filtered water tastes better. So all my pets and I drink filtered tap water.
