Your water bottle could be harbouring a horrifying secret - Health

Nov 19, 2025

Your emotional support water bottle might need some support of its own.

Got your water bottle with you today? Of course you do. They’ve become such a ubiquitous part of our daily lives, they’re now as automatic to grab as your keys and phone when you leave the house. The water bottle has even become something of a fashion statement, with brands like Stanley garnering cult followings. But how often do you clean yours? After reading this, you might think twice before your next sip.

Back in 2017, researchers at Purdue University in the US tested 90 reusable water bottles in a variety of designs and materials, and found they were a hotbed of bacteria – most had high to unsafe levels of bacteria in them.

Stanley cups — If you don’t own a Stanley cup, do you even deserve to drink water?

If you want numbers, a 2022 study by WaterFilterGuru.com found that reusable water bottles contain an average of 20.8 million colony-forming units (CFUs – the number of viable microbes that can grow and multiply on a surface). There were two main types of bacteria present: gram-negative rods – which can cause infections that are becoming increasingly resistant to antibiotics – and bacillus, which can cause gastro.

Spout-top and screw-top lids contained the most bacteria, with 30 million CFUs each.

They also found that on average, a reusable water bottle had 40,000 times the bacteria of a toilet seat.

Another study at the Indiana University School of Medicine, US, found that a 10-year-old’s Stanley cup contained staphylococcus and coliform bacteria – respectively, that’s the bacteria that causes staph infections and, well, poop. More than 20 percent of the Purdue University study samples contained coliform bacteria.

Hmmm. Not looking so refreshing now, is it?

washing water bottle — Your water bottle is like any other drinking utensil – it needs regular cleaning.

How to clean a water bottle

Before cleaning, be sure to take the lid and any other components, like a straw, off to wash separately. If your bottle is dishwasher safe and has a wide-enough opening for the dishwasher jets to get inside, you can wash it in your dishwasher, placed on the top shelf. Give it a good rinse out beforehand, and let it dry completely after washing before reassembling.

To wash your bottle by hand, take it completely apart, and use hot water (over 60°C, as this will kill most germs) and washing-up liquid. For best results, use a bottle brush to thoroughly clean the inside, and use a clean toothbrush to clean the mouthpiece and around any crevices. Rinse thoroughly with hot water, then let it dry completely before reassembling.

If it’s been a while between washes, fill the bottle with half cleaning vinegar and half water and let it soak for a few days. Or fill with hot water and a tablespoon of baking soda and let it soak overnight. You can also soak any components in a solution of either. After soaking, follow the washing method outlined above.

Georg Jensen SKY water bottles are made from stainless steel.

How often to clean a water bottle

You should rinse your bottle at least once a day – always empty your bottle at the end of the day and rinse before refilling – and wash it once a week. Always let your bottle dry completely after washing. It’s important that you also rinse and clean any lids and attachments this often as well.

What is the most hygienic water bottle?

The best choice is a stainless steel or glass bottle with a wide mouth. Stainless steel and glass don’t harbour bacteria like plastic does, while a wide mouth makes the bottle easier to clean and dry, and reduces the number of hidden crevices where bacteria can lurk.

Along with nooks and crannies, if your bottle has a lot of moving parts that require you to touch to access the water – like a pop top, a button lid or a flip-out straw you need to use your fingers to invert – you’re also passing any bacteria from your hands to the bottle.

Straight straw-top bottles can reduce the amount of bacteria present, as water drips back down into the bottle after you sip, instead of remaining on the mouthpiece. But straws also require careful and thorough regular cleaning.