You take it to work, sip on it at the gym, and refill it again after dinner. Your water bottle is in tow wherever you go, but how often are you washing it?

Bacteria festers in our water bottles and it’s our job to keep them clean with regular washing and rinsing.

“People make assumptions that because it’s only water and only they use the bottle, that there is no risk. Bacteria and other microbes can accumulate in the bottle — forming biofilms on the surfaces — and also on the opening of the bottle that is in contact with the mouth and hands,” Dr. Elizabeth Scott, a biology professor at Boston’s Simmons College, told Global News.

“Think about it — you need a few things for micro-organisms to grow: a warm environment, nutrients like food or saliva and water. That’s all around your water bottle,” said Jason Tetro, a Canadian microbiologist and bestselling author.

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The average water bottle has about 313,499 CFU (or colony-forming units of bacteria) compared to 2,937 CFU on a pet’s chew toy, according to a recent TreadmillReviews.ca study.

The organization swabbed 12 water bottles. They found that:

Slide-top water bottles carried the most germs at 933,340 CFU

Squeeze-top bottles had 161,971 CFU

Screw-top bottles had 159,060 CFU

Straw-top bottles had only 25.4 CFU

“The spot your lips touch is absolutely writhing with bacteria: over 900,000 CFU/sq cm on average,” the report warns. Tweet This

It estimates that 60 per cent of the germs found can make people sick.

Scott and Tetro suggest it’s far less, though.

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“Most are probably harmless environmental microbes but also some potentially harmful germs or pathogens, such as bacteria,” Scott said. She pointed to staphylococci and streptococci (strep throat), and viruses, from cold and flu viruses to mononucleosis, meningitis, mumps, herpes, and norovirus as potential germs that could cause harm.

“Very little to none are going to be pathogenic to you. They’ll be gross and as it goes on and grows, you might find your water tastes different,” Tetro said.

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And growth happens quickly, too. Most germs establish themselves and survive on wet surfaces. They can replicate within hours.

Within a few days, your bottle could develop a biofilm, especially on the bottom where people rarely thoroughly get to clean.

If you’re sharing, you’re more likely to swap germs. And if you’re adding cucumber, lemon or berries to your water, count on those ingredients to increase your chances of growing bacteria in your canister.

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So how often should you wash your water bottle?

The experts suggest reusable water bottles should be washed each time after use. Tetro said you can rinse your bottle with hot water over 71 C. With temperatures of about 55 C, use soap with some kind of cloth or sponge and make sure you’re giving your bottle a thorough rinse.

Dry your water bottle after that. You can also throw it into the dishwasher, Scott said.

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“It’s a little weird that people miss this when they would be unlikely to keep using a tea or coffee cup, for example, without washing it. Bottles can become contaminated from the water source itself and from the mouth and the hands,” she said.

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“We want people to get into the habit of cleaning their bottles. You’re pushing it after only two or three days,” Tetro said.

carmen.chai@globalnews.ca

Follow @Carmen_Chai