Listen. I am all for going green, but ever since my science teacher told me that tap water could be contaminated with chemicals not caught by filters, I stick with my water cooler.
Here is an article on Yahoo that discuss the safe and not so safe types of tap water: http://green.yahoo.com/blog/the_conscious_consumer/134/the-experts-take-on-tap-water-safety.html
Oh, and if you’re wondering about the water cooler; you can buy one or rent one, and then the jugs are usually delivered every two weeks. It’s worth it.