EXTRA: Don't re-use plastic water bottles

St. Petersburg, Florida - Every day people work hard for a healthy body. And during those workouts, it's important to double or even triple your water intake.

Kellie Pioch is a personal trainer. She always has a bottle of water by her side when exercising. “If I drink it, I just refill it up,” she explains.

Victoria and Robert Saunders also reuse their bottles, but they prefer buying filtered water as well as bottles from a company, then clean them daily.

In fact, we found lots of people refilling plastic water bottles at the gym. Even though it's important to replenish fluids, doing this could also increase your chances of getting sick.

University of South Florida Professor Burt Anderson says people should be careful. “It's safe as long as you don't use them too much.” Anderson says people with weak immune systems should avoid re-using plastic water bottles because of bacteria that can potentially cause infection.

We decided to find out by testing 10 plastic water bottles for bacteria. We collected the bottles from our own newsroom and St. Anthony's Wellness Center. Hugh Rodrigues of Thorton Labs gave me the bad news: my bottle had 500 colony forming units (CFU's) of bacteria. Not too healthy.

“Basic hygienic practices may not have been followed, the bottles may not have been rinsed properly prior to a continued use,” Rodrigues says.

He's right, I never rinsed out the bottle, because I was still drinking the original water over a few days.

Another co-worker had 3,400 CFU's after using his bottle over a four day period. And remember Victoria from the Wellness Center?

Well Rodrigues says, her special water bottle was way over the acceptable limit of 10 CFU's. She had 650,000 colonies of bacteria.

“Now that's really bad, that there is very much cause for concern.”

Depending on what type of bacteria it is, Rodrigues says someone could get sick. “Basic symptoms would be nausea, some diarrhea, some cases vomiting and all of those would be based on the type of bacteria that was present.”

But it's tough telling what kind of bacteria it is. “It could be coliforms, which you start to get into dangerous situations there or it could just be yeast and mold type spores, which are common in the air.”

In order to prevent bacteria from building up in water bottles, you can put them in the dishwasher or wash them with warm soap and water.

Disposable bottles should be thrown away after one or two uses.

Kellie the trainer had 270 bacteria colonies, which could be risky.

Experts say you should also avoid sharing water bottles, even with your spouse. So by taking the right steps, you could protect yourself from getting sick.