Don't buy bottled water.
I happen to live in a town that sends me a little pamphlet now and then about the quality of my water and how it compares to EPA standards. Harrison's water is just fine. Though I do normally detect a Chlorinelike taste right out of the tap.
If you are worried about pollutants, get a brita or other filtering unit. It will save you tons of money and you will still keep plastic bottles out of landfills or at the very least save some energy in terms of not buying somthing that was transported on a dirty diesel truck, that wasn't refrigerated at a store (costing energy) and wasn't recycled. Cuz even recycling spends energy. What do you think melts the bottles?
In any case, I just performed my own little experiment with water. I made my first batch of homebrewed amber ale (currently debating wether or not to start another blog about homebrewing). I used regular Harrison tap water. I told my fiancee and my friends it was bottled. They said the beer tasted great. I think the beer tastes great too. Since beer costs money to make (albeit less money than buying already made beer) adding the bottled water to the cost just takes that much more off of my savings.
My second batch was a stout made with bottled water. It isn't ready to drink yet but I tasted the uncarbonated version yesterday. Alec Guiness himself would be hard pressed to find a taste difference. Granted I only used the bottles because the fiancee is paranoid about the water. However, if an amber ale can easily mask any "flavor" my water could have contributed, why not the murky dark choclatey goodness of a stout?
In short, drink tap water, if you freak about your water or if you know your water to be polluted, get a filter. However, by all means, stop drinking bottled water. It is Un-American at best and aiding and abbetting terrorists at worse.