1. Tap water is tested daily
Under the Safe Drinking Water Act, water suppliers are required to provide an annual report on the quality of your local water and to test tap water daily. By comparison, the FDA examines bottled water only weekly, and consumers can’t get the agency’s results. You can easily get the lowdown on your state’s drinking water quality at  http://www.epa.gov/safewater/dwinfo/index.html. Do you know really know where your bottled water comes from?

2. Tap water is a bargain 
Bottled water costs about 500 times more than tap. If you’re into really fancy labels, up to 1,000 times more.

3. Tap water is a tooth saver
It has more fluoride than bottled water, which helps prevent tooth decay. (Yes, you never outgrow your need for fluoride.)

4. Tap water is often tasty
Some places (New York City for one) have delicious water, but if you don’t love the flavor of yours, the solution is simple: Run your tap water through a Brita or Pur filter to remove most tastes and odors. The average home filter goes for $8.99 and produces the equivalent of 300 large (16.9 ounce) bottles of water. That’s about $0.03 cents a bottle, versus the $1.25 or so you’d pay in a market. Tests have shown that most people prefer tap water in blind taste tests, or simply cannot tell the difference.

5. Tap water is better for the environment
Glug, glug, glug--that’s the sound we make as we sip bottled water in our cars, at the gym, behind our desks. The sound you DON’T hear is the thwack of 60 million bottles a day being tossed into U.S. landfills, where they can take up to 1,000 years to biodegrade. If that’s not enough to turn your conscience a brighter shade of green, add this: Producing those bottles burns through 1.5 million barrels of crude oil annually--enough fuel to keep 100,000 cars running for a year. Recycling helps but reusing is even better. Invest in a couple of portable, dishwasher-safe, stainless steel bottles like Klean Kanteens that won’t leach nasty chemicals into your water. (Don’t get into the habit of refilling the water bottle you just emptied; the polyethylene terephthalate it’s made of breaks down with multiple usings.)

Bonus: While you are considering the greener side of things, stop using plastic bags at the market. I have been using the same three paper sacks at the grocery store for over a year. Most chain grocers will even give you a discount for reusing paper bags. At my Kroger, I get 5 cents off for every reused bag, every time I shop. Throw the bags in the trunk of the car after putting away the groceries at home, and you'll have them the next time you shop. Some cities are outlawing plastic bags. If the places you shop do not have anything but plastic bags, take your own bags with you. If "style" is an issue for you, there are thousands of cloth tote bags on the market.