I don't find the water fountain water being that bad. I fill up my unfiltered water bottle all the time. Definitely don't go to one that has been in the sun. The one at the top of the hill at the International Gateway is one to avoid. The water fountain near the Off Kilter stage in Canada is probably the best one. Yes, I fill up enough to know which ones are good ones.
Just a suggestion that I do myself after having to wait for a lady to fill up ten bottles for her family. Please use the lower water fountain to fill up your bottle(s). MOre adult than kids use the fountains so you are leaving the higher one available for the taller people. Just a suggestion - it's the same water.