You’re probably not washing your water bottle often enough

It's essential to learn how to wash your water bottle properly.
Person holding laptop and a white reusable water bottle.
How filtered is your water doesn't matter that much if your bottle has more germs than a trash can. Bluewater Sweden / Unsplash

They started out as a great alternative to reduce plastic waste, and now thanks to social media, reusable water bottles have become a fashion accessory with a cult-following. But no matter how much you splurged on yours, you’re in for some bad news: it’s likely full of germs.

This might seem counterintuitive since most of us are only filling our bottles with drinking water. But a 2017 study published in the ​​Annals of Civil and Environmental Engineering found that an adult’s reusable water bottle can contain around 75,000 bacteria. That’s a lot more than the average toilet seat.  

So before you take another sip, it’s time you learn how often to clean your water bottle and how to sanitize it correctly.

Bottle ‘o bacteria 

Different types of bacteria, mold, and fungi can make an appearance in your water bottle—and you’re the source of many of them. Charles Gerba, a microbiologist and professor of virology at the University of Arizona, says you can transfer bacteria from your mouth to your bottle every time you take a sip. This includes Staphylococcus aureus, for example, which can cause ailments ranging from skin infections to pneumonia. The same goes for viruses like the flu, mononucleosis, and type 1 herpes, some of which can carry over to your water bottle even if you don’t have symptoms

[Related: The germiest places you might not be cleaning]

The germs you transmit when you sip are generally harmless, Gerba says, but if your hands are dirty, you can easily contaminate your water bottle with bacteria like E. coli, which can cause gastrointestinal issues if you ingest too much of it. 

These germs are also the reason why it’s never a good idea to share water bottles. Gerba explains that your immune system is used to the microorganisms living in your mouth and throat, but any invaders might cause it to react and make you sick. Sticking to your own bottle will prevent you from catching or passing on diseases that spread through saliva, keeping you and others safe and healthy. 

Don’t forget about mold

But bacteria is not your only problem: your water bottle can also grow all types of mold. Stachybotrys chartarum, also known as black mold, is the most common, says Jennifer Nitrio, a certified mold inspector and owner of Mold Help for You

“This is because [black mold] loves moist, dark environments,” she explains. It also likes warmth, so conditions get very attractive to Stachybotrys when water bottles end up in hot cars or locker rooms.

Mold also needs food to thrive and your mouth’s bacteria, now relocated in your water bottle, offer the perfect feast, says Nitrio. To make things worse for you (and cozier for mold) these microorganisms love sugar, so filling up your bottle with sweet beverages will only increase their chances of growing. 

Finally, what your water bottle is made of also plays a part in mold growth, but it’s not as important as you’d think. Nitrio explains plastic tends to grow mold slightly faster than other materials, but “90 percent of the time mold occurs because of improper water bottle hygiene, which means it is just as likely to grow on glass as it is plastic or metal.”

Needless to say, ingesting even a small amount of black mold will ruin your hydration ritual, as moldy food or water just tastes bad. But depending on how sensitive you are, it could also lead to poisoning, which entails symptoms like body aches, headaches, and nosebleeds

Clean your water bottle often and thoroughly 

There is hope for anyone worried about a dirty water bottle and it’s simple—just wash it. Gerba recommends you clean yours every day or at least once a week. And don’t just simply rinse it out: It’s important to give it a proper wash. 

If your water bottle is dishwasher safe, Gerba says running it through a sanitizing cycle should kill all bacteria, but usually, a normal one should do the job just fine. Otherwise, investing in a specialized brush set can make cleaning your bottle easier by helping you get to any tough-to-reach spots. Don’t forget to use a pipe-cleaner brush (they’re usually included in these sets) to help give your straw or mouthpiece a proper clean. 

[Related: Your smartphone is gross. Learn how to clean it properly.]

Nitrio recommends getting rid of some germs first by filling your bottle with hot water and a tablespoon of white vinegar and letting it sit. Once you can safely and comfortably touch the outside of the bottle with your hands, carefully close the top and give it a good shake. After that, open the bottle, rinse it out, and use your brushes to give it a normal wash with soapy water. 

If you don’t have vinegar on hand, you can also use bleach diluted in water to quickly get rid of any germs that might be lurking. The Centers for Disease Control and Prevention recommends a solution of five tablespoons of bleach per gallon of water, and if you don’t feel like making that much, you can always scale down the recipe by diluting four teaspoons of bleach per quart of water. To clean your water bottle, spray the solution all over it, or pour it into a large bowl and submerge the bottle in it so that it floods every nook and cranny. Let it sit for a couple of minutes and finish things off by rinsing the bottle and washing it with water and soap. 

When you’re done with your wash, you can dry it off using a clean paper or dish towel. If you’re air drying, let your water bottle sit without the cap on to prevent the accumulation of extra moisture, as it can trigger mold growth. 

Keep in mind that as long as your emotional support water bottle is clean, you don’t have to worry about it not loving you back.