How Often Should You Actually Clean Your Reusable Water Bottles?

Here's the dirty truth.

A person holding a blue water bottle next to a running faucet

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There’s a good chance you aren’t washing your reusable water bottle often enough. Whether you have it sitting at your desk while you work or along for the ride as you hit the gym, your water bottle is constantly collecting and growing gross germs.

“The inside of a water bottle is the perfect damp environment for germs or mold to spread,” says Jessica Ek, spokesperson for the American Cleaning Institute. “Eventually, that could make you sick.”

Counting Water Bottle Germs

In a study by Treadmill Reviews, researchers swabbed a dozen water bottles that were being used by athletes that hadn’t been washed in a week. They tested screw-top, slide-top, squeeze-top, and straw-top models and found that they had more than 300,000 colony-forming units per square centimeter (CFU/sq cm). To put that into perspective, that’s about six times more than your dog’s water bowl (47,383 CFU) and just a little less than the toothbrush holder sitting in your bathroom (331,848 CFU).

Slide-top bottles where you just slip the lid open and closed by far had the most germs, while straw-top bottles were surprisingly much lower than other types. The straw-top bottles tested had just 25 CFU of bacteria, likely because “water drips to the bottom of the straw rather than sticking around to attract moisture-loving germs.” However, the testers point out that that's only 2 CFU less than a home toilet seat.

How Often You Should Wash Your Water Bottle

Do you toss your bottle every once in a while into the dishwasher or rinse it when you think of it? That’s nowhere near often enough.

You should wash your water bottle after each use. If you’re using it and refilling it throughout the day, you should wash it at the end of the day. “After a week, that water bottle has more bacteria than a pet bowl,” says Ek. “After a month? That’s a lot of opportunity for germs to spread.” 

How to Wash Your Water Bottle

First, check the label or look at the manufacturer’s site online. Many reusable water bottles can be cleaned in the dishwasher. Often you need to put any caps in the top rack. You still need to do that after each time you use it.

To wash by hand, here’s what Ek suggests:

  • Fill the water bottle with water and dish soap. 
  • Soak the other pieces—like a lid or any straws—in a bowl of soapy water. 
  • If you have a bottle brush, use it to scrub the inside of the bottle and all the hard-to-reach spots in the lid.
  • Rinse everything thoroughly and dry. It can help to turn it upside down to let all moisture seep out.
  • Make sure it’s completely dry before putting it back together or it could become musty.