A mug full of bugs

Next time you find yourself battling a stomach bug, don't automatically blame it on something you ate -- because it may have been something you drank.

The fact is, your drinking water isn't nearly as clean as it looks. And now, a new study finds that ordinary tap water could be responsible for up to 1.1 million cases of the runs every single year in the United States alone.

That's up to 20 percent of all stomach problems in adults and as much as 40 percent in kids -- all from something that most people take for granted.

Millions of Americans get their water from aquifers, underground pools where the surrounding rock can filter the water and keep it clean and free of bacteria. And if you were able to poke a straw through the ground and pull the water up through that rock yourself, it might even be clean. (Clean of bacteria; other pollutants are a growing problem -- and a story for another day).

The problem comes after the water is removed -- when it has to pass through dirty and leaky pipes that often run alongside sewer pipes that aren't in the best of shape themselves.

You can see what's happening here, right? The germs from the sewer pipes can end up in the water pipes. Turn on your sink, and they're in your water glass.

Next thing you know, you're fighting off a stomach infection, never suspecting it came from your drinking water.

Better water treatment plants won't help, since these problems can happen in the pipes that bring the water from the plant to your home. And that means it's up to you to keep your water clean -- and not just free of the bacteria leaking out of sewer pipes.

U.S. drinking water can contain drugs, hormones, chemicals, and more -- and, as I told you a few weeks ago, a deadly brain-eating amoeba has even been found in the water in one part of the country.

The two best ways to keep your water clean are with a reverse osmosis water filter or a water distiller, and you can find both online or in your local hardware store.