Do you just refill your water bottle or mug? “I just put water in it. It isn’t dirty!” Sometimes we just kind of swish it under running water and we think we’re good to go.

But even if we only use our water bottle to just drink water it can still hide a lot of germs.

Airborne microbes such as bacteria, viruses and fungi can cling to the water spout or your mug. And by the way, these germs thrive in damp, humid environments like airconditioned offices or the dryer in your kitchen. (We don’t even want to think about the type of germs that live in our gym bags.)

Microbiologist Miryam Z. Wahrman, Ph.D — a biology university professor and author of The Hand Book: Surviving in a Germ-Filled World,  says that’s not the only thing that’s floating in our water. We also transfer bacteria and minute traces of food, makeup or whatever was in our mouth to our bottles and mugs.

So now we have bacteria, fungi, food particles and makeup residue in our supposedly “clean” water bottle or mug. Gross! Here are other habits that contaminate your water bottle.

Leaving bottles or mugs in hot areas

“Living microbes just adore water and warm temperatures,” says Wahrman. That includes a desk by the window, in your car, your gym bag.

Sharing water bottles

Sharing may be caring, but not when it comes to mugs or water bottles. Even family members should have their own (buy them in different colours). This also prevents passing any colds or other viruses.

Not tossing old water

At the end of the day, empty your drinking container and wash it with dish soap and water. Let it dry out. Never, ever just take yesterday’s half-filled bottle and just add more to fill it up. If you’re wary about wasting water, pour it into another container to use for cooking or watering the plants.

Not deep-cleaning your water bottle

Once a week, fill your hot water bottle and give it a really thoroughly clean with a bottle brush, warm soapy water, and baking soda. The baking soda will also help get rid of any stale smells.

Don’t forget to clean the water spout and the little ridges and corners around the cap! If it has a rubber seal ring, remove it and give it a good scrub too. You can also use rub it with slice of lemon (a natural disinfectant).