By Amanda Weston

After making a name for himself in the pool, Olympic gold medalist Michael Phelps is making it his mission to save water in American homes.

Phelps, now working with Colgate as a Global Ambassador, told Cheddar that in the next decade, 40 U.S. states will be in a "massive crisis."

"I'm just asking people to use common sense," Phelps said Wednesday. "Everyone's probably in so many habits where you're used to having the water running while you're brushing your teeth, or taking a longer shower. Just some of those small things, we really can make a huge change for the kids coming up."

The average American family uses more than 300 gallons of water per day at home.

By leaving the faucet on while brushing his or her teeth, the average American can waste up to four gallons of drinking water in two minutes.

Phelps said simply turning the faucet off can make a huge difference.

"My son is two, about to be three, and he can do it," Phelps said. "So why can't anybody else? Why can't everybody else? There are so many little, small things that we can all do, like I said, that make a huge difference for generations to come, and it's just a precious resource that we need to conserve as much as we can."