The argument also for tap water is that bottled water is no better... hmmm... and this I have to say : Yes, if you buy bottled water from companies owned by Coca Cola you are getting filtered tap anyway, so don't support a crazy cooperation selling bottled sink water. The other issue to check with bottled water is UV filtering. UV filtering causes ozone which in turn kills bacteria, the water has to be blasted with so much bacteria killing ozone that if a human being were to breathe the amount of UV air used they would suffocate to death. The reason most bottled spring water has strange chemicals in it once tested is due to these ozone molecules breaking down, once they break down they begin to adhere themselves to other molecules- and voila, any chemical reaction is possible! This typically creates a bunch of nasty aldehydes...super yuck!
So if you rather indulge in the tap revolution, make sure you stick a filter on it... a good pricey filter that will last a long time- just like you want your body to do. And if you drink bottled water instead read the labels for UV filtering (Fiji and Volvic do not UV filter their water), and make sure to recycle those plastic bottles- or fill them with sand and build a eco hut out of them, or start a plastic bottle chandelier boutique... be creative with your trash !
To find quality water filters and water conservation gear for your tap try Real Goods @ http://www.realgoods.com/category/home-outdoor/water-quality-conservation.do