Problem: Of course you want to cool off after working out, but water fountains are perhaps one of the grossest offenders in the gym when it comes to germs. I wouldn't even suggest filling your bottle there. People's mouths regularly come in contact with the water fountain, and, so do the lips of their water bottles if they refill them at the fountain. A study done by Coverall Cleaning found more germs on water fountains than it did on toilets.
Solution: Always bring your own water bottle to the gym, and, make sure that it's already filled. If you must drink from the fountain, be sure to not let your lips come into contact with the fountain itself. Also, wash hands after touching the drinking fountain.