Apparently I am one, because I just top off the tap water throughout the week then do a full change out on the weekend when I clean cages. I dump the water in a large tub or bucket, clean the bowl, scrub if needed, rinse, disinfect with bleach, rinse, dry, and refill. I sometimes use the discarded water to water plants in the house or yard. Yes, I know this could cause salmonella transmission, but since I am not supposed to chew on my Pothos plant anyways, I am not terribly concerned.
AND, I use tapwater.
Having said that, our water is pretty nice. We get an extensive report of what is put in and not put in the water, nitrate levels, hard water test, etc. The water does come with chlorine in it, but we let the fresh water sit most of the week before we do changes. We keep a turtle and some fish in the same water with NO ill affects. Many other keepers here in town do the same thing. My mice also drink the same water and all I can say about what chemicals might be in it is the Florine definitely makes sure their teeth are hard and sharp (Ouch!....j/k). My domestic mice rarely get tumors or UTIs which are some of the most common causes of spontaneous death that I know of in colonies (other than introduction to Ball Pythons) so that is a note of confidence for our water supply.
If you are that concerned about your tap water versus bottled you could have a test done on your water. Most local universities will perform them for a nominal fee. Many places that handle hard-water issues and install water heaters can also perform the tests.
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Lincoln, NE
Ball Pythons - 0.1 Pastel, 1.0 Pastel het Pied, 0.1 Pied, 0.1 Cinn, 1.0 Black Pewter, 1.0 Woma (hidden gene?), 0.1 Yellowbelly
2.1 Normals
Kingsnakes - 1.0 L. m. thayeri, 0.1 L. m. thayeri X L. alterna, 1.0 L. g. californiae
Other - 0.1 Whitesided P. catenifer sayi, 1.0 H. nascicus, ?.? Chrysemys picta, 0.1 crazy cat, 1.0 husband