The Envirnmental Working Group just released a study of major bottled water brands that is worth a look.
"Unlike tap water, where consumers are provided with test results every year, the bottled water industry does not disclose the results of any contaminant testing that it conducts. Instead, the industry hides behind the claim that bottled water is held to the same safety standards as tap water. But with promotional campaigns saturated with images of mountain springs, and prices 1,900 times the price of tap water, consumers are clearly led to believe that they are buying a product that has been purified to a level beyond the water that comes out of the garden hose.
To the contrary, our tests strongly indicate that the purity of bottled water cannot be trusted. Given the industry's refusal to make available data to support their claims of superiority, consumer confidence in the purity of bottled water is simply not justified."