Your Water Bottle May Be Growing Mold: Here’s How To Prevent It

We all know the pros of using a reusable water bottle. It’s good for the environment, easy to carry and lets you drink enough water instead of refilling your glass. And while your water bottle can help you stay on top of your hydration, you should also stay on top of cleaning it.

You may assume that since you’re just using your water bottle for water, there’s no risk of contamination. What’s cleaner than H20, right? But mold and bacteria can sneak their way into your drinking water right under your nose.

Internal medicine physician Marianne Sumego, MD, explains how to prevent your water bottle from becoming a hub for mold and bacteria.

Is it possible for mold to grow in my water bottle?

In short, absolutely. Your emotional support water bottle can quickly become a warm, cozy home for mold.

“Certain bacteria and molds depend on water,” explains Dr. Sumego. “Places like lakes or ponds become breeding grounds for bacteria to replicate. And in some cases, you end up with enough bacteria to get an infection if you drink the water.”

But mold and bacteria don’t just occur in nature — they can also creep up and take residence in many spots around your home. That’s why even your bathroom or shower can have mold problems.

Our water bottles are no exception. Think about it: When was the last time you emptied your water bottle? Most of us keep liquids in them all day, every day. Because of this, they rarely dry completely.

And without proper cleaning, your water bottle can become an ecosystem of mold and bacteria. This is thanks to its dark, moist and warm inside. It might start as tiny specks you can barely see. But if left unchecked, they can grow and contaminate the water you’re drinking.

Health risks of consuming mold

Even though some foods, like cheese and mushrooms, are in the mold family, that doesn’t mean all mold is safe to consume. Ingesting mold can have certain health risks, especially if you consume it for long periods of time or are sensitive to it.

“When you find yourself with minor illnesses, such as nagging respiratory symptoms that aren’t improving, it may be tied to things you’re not cleaning,” Dr. Sumego says.

Health risks of consuming mold include:

• Stomach issues. Mold can irritate your stomach and digestive system. If you accidentally drink water with mold in it, you might feel sick to your stomach, get stomach cramps or have diarrhea.
• Allergic reactions. Some people are allergic to mold. Even a small amount of mold can trigger allergic reactions like sneezing, coughing, itching or a runny nose.
• Respiratory problems. Breathing in mold spores (tiny particles that mold releases into the air) can cause respiratory issues, especially if you have asthma or other lung conditions. It can make it harder to breathe and lead to coughing or wheezing.
• Infections. In rare cases, mold can cause infections, especially if you have a weakened immune system. This is more common with certain types of mold, like black mold.

“You might get a very mild case or something a bit more severe,” Dr. Sumego notes. “But if you’re at higher risk, repeated exposure to mold or bacteria can be more harmful and serious.”

How do I know if there’s mold or bacteria growing in my water bottle?

Despite its reputation, mold may not always be obvious. As Dr. Sumego points out, the first signs of mold may be a more subtle, slimy texture.

“If you’ve ever let your bottle get to the point where there’s a thin film — it’s called biofilm — that’s a sign that bacteria and mold are building up,” she says.

The best way to figure out if your water bottle has mold is to follow your senses. Here are some things to look out for:

• Visible spots. One of the more obvious signs is seeing actual mold spots inside your water bottle. They might appear as fuzzy or slimy patches, usually green, black or sometimes white.
• Unpleasant smell. If you notice your water bottle smells funny, even after you’ve washed it, there could be mold lurking inside. The water inside may start to give off a musty, slightly earthy smell.
• Cloudy appearance of water. Mold can sometimes make the water in your bottle look cloudy or murky. If your water doesn’t look clear and clean, it could be a sign of mold growth.
• Residue or film. Mold can leave behind a residue or film on the walls of your water bottle. If you notice any strange textures or coatings inside, it could be mold-related.
• Unpleasant taste. Mold can also affect the taste of your water. If your water tastes strange or unpleasant (again, even after you’ve washed it), it might be due to mold contamination.

What to do if you find mold in your water bottle 

If you find mold in your water bottle, don’t panic. If you’ve only taken a few sips, you likely won’t experience any side effects. But everyone is different and could react to consuming mold differently, so pay close attention to how you’re feeling afterward.

First thing first: Stop drinking from the water bottle immediately. Then, it’s time to get cleaning! 

You can start by disinfecting your water bottle with hot water and soap. A 2015 study also found that vinegar can help stop mold growth. To kill mold spores, you can use a vinegar solution (equal parts vinegar and water) in the water bottle to give it a deeper clean. Let the disinfectant sit in the bottle for a few minutes before rinsing it out thoroughly. (More on proper cleaning next.)

Finally, be sure to clean your water bottle so it dries completely. Remember, mold loves those damp environments.

How to properly clean your water bottle

Whether you’ve found mold or you want to prevent mold from forming in your water bottle, you’ll need to do more than just throw some water in and swish it around. “Once a week, you really want to run it through the dishwasher,” Dr. Sumego suggests. “That way, you get enough hot water in those nooks and crannies.”

If you can’t use a dishwasher, hand washing will do the trick, too. Here’s the best way to clean your water bottle to avoid mold growth:

1. Empty your bottle. Make sure your water bottle is empty before you start cleaning it. Pour out any leftover water.
2. Break down your water bottle. If your water bottle has removable parts like a lid or straw, take them apart. This makes it easier to clean the little crevices. “We’ve all got those water bottles with the slide mouthpiece, the straw, all those areas that aren’t easy to reach,” Dr. Sumego says. It’s important to break each part down to its separate pieces. You won’t be able to prevent mold growth if you keep the silicone gasket inside the slider, still attached to the lid when you wash it. Check your owner’s manual to see how you can remove each component.
3. Rinse thoroughly. Rinse your water bottle with warm water to remove any leftover liquids or residue.
4. Use soap and scrub. Put a few drops of liquid dish soap into your bottle and onto each piece. Using a bottle brush or sponge, dip it into the bottle and scrub the inside. Individually scrub each component as well. Pay attention to areas where mold or bacteria might hide, like the cap or around the mouthpiece.
5. Use vinegar for an extra deep clean. If you want to do an extra deep clean (let’s say it’s been a minute since your water bottle had a good scrub), try the vinegar solution mentioned above.
6. Rinse. Give the bottle and each part a thorough rinse with hot water to wash away the soap.
7. Dry completely. After rinsing, shake out any excess water and leave your water bottle to air dry completely. This helps prevent mold from growing again.

Preventing mold growth in your water bottle 

So, how often should you be cleaning your water bottle to prevent mold growth? According to Dr. Sumego, you should give your water bottle a deep clean — breaking it down into parts like we mentioned — at least once a week.

On a daily basis, Dr. Sumego recommends at least rinsing out your bottle using warm water after every use. If you want to be extra safe, you can give it a quick wash with dish soap after every use as well (even if you don’t break it apart).

This will prevent your water bottle from growing mold and other types of bacteria from getting in your drinking water.

“People forget that we have bacteria in our mouths and hands,” Dr. Sumego states. “So, every time we touch and fill our bottles, set them down or take the caps off, we introduce bacteria.”