How Often Should You Wash Your Thermos?

I love my Thermos bottles and food containers as they keep drinks hot or cold for hours at a time.

Whether it's packing soup for lunch on a cold day or using my thermos water bottle to drink more water each day – they work really well.

While I would wash the food canisters after ever use, being a lazy washer I would often leave the water bottles a few days between cleanings. Then it started to develop a funky smell and I suspect I was drinking from a moldy water bottle.

Eventually I worked out how often I should be washing my thermos bottles and with the right bottle brush it's fairly easy to consistently do.

Thermos bottles and food canister should be washed at least once per day and after every use if you're putting anything other than water in them. You may be able to stretch water bottles to once every few days but if you even notice a strange smell or taste then you should treat your bottle for mold immediately and give it a deep clean with vinegar.

I found out the hard way that just rinsing out your thermos isn’t enough.

In order to prevent bacteria from growing you need to wash your bottle properly. I advise getting a good bottle brush that makes it easy to clean your bottles.

I recommend this affordable 3-in-1 bottle brush from Amazon. It works great for me as the long handle makes it easy to get inside even the big thermos bottles and the smaller brushes are great for cleaning the thermos gaskets so they don't grow mold.

You Should (Ideally) Wash Your Thermos Daily

You should ideally wash your thermos bottle after every use, or at the very least you should wash it every day if you're refilling it throughout the day.

The inside of your thermos is the perfect breeding ground for bacteria and other germs. If you don't wash it regularly than these will grow, even if you're only placing water in the bottle.

But let's be real here. Most of us don't really want to wash our bottles a few times per day.

If you're only drinking water, then once per day is the ideal amount of time to wait between washes. You can go a few days without washing your bottle. However, you shouldn't do this regularly because mold will grow over time.

If you decide not to wash it, then you should at least give it a rinse and then leave it upside down and open to air dry overnight. Less mold will grow in a dry water bottle, then in a wet one.

What Happens If You Don't Wash Your Thermos Enough?

well, you might think that your thermos is fine to drink out of if you're not cleaning it regularly overtime a layer of scum and mold on the inside of the bottle will begin to develop.

Most often you will smell this well before you see it and I recently just noticed that one of my bottles smells a bit moldy.

If your bottle has any sort of funky smell than a simple wash with soap and water won't be enough to kill and clean the mold.

You should use one of these techniques for getting mold out of a water bottle or use one of these techniques for cleaning narrow mouth water bottles.

Deep Clean Your Thermos At Least Once a Month

On top of your regular daily washes, it's also a good idea to give you a thermos a deep cleaning every month also.

This will help to prevent mold or kill any mold that has started to grow in your bottle. It will also kill any stubborn germs or bacteria, and will stop the build up of bio film on the inside of your bottle.

To deep clean your thermos check out the different options below:

A Few Ways I Like To Clean My Thermos Bottles

Depending on how diligent you are with cleaning your thermoses and how dirty they are you might want to use some different cleaning methods.

If I'm good and just use water in my thermos then the simple clean with soap and water does the job.

However, if I've been lazy and left water or smoothie or soda in my thermos and haven't cleaned it quickly then usually I find it needs a deep clean to kill any mold and bacteria growing in there.

Washing Your Thermos With Soap and Water

This is my go to method for everyday cleaning and a good bottle brush like this affordable one from Amazon is a must to make cleaning the inside east and efficient.

One of the most basic methods for washing your thermos is with dish soap and hot (or at least warm) water.

Fill the thermos around half way with the soapy water, screw on the cap, and shake the thermos for a few seconds.

Next, pour out most of the water, but leave a little to use on the bottle brush.

Scrub the inside and outside around the lip, as well as all over the lid, with the brush and soapy water.

After that, rinse everything off until you don’t see any more suds and leave to air dry. You can also use a paper towel or a clean cloth if you’re in a hurry.

Washing Your Thermos With Vinegar And Baking Soda

Fill your thermos 1/4 with vinegar, 1/4 with warm water and add a teaspoon of baking soda into the mix.

Give the bottle a shake so the mixture coats all walls of the bottle and then leave the bottle overnight.

In the morning rinse it out thoroughly with warm water. It’s perfectly safe to use this amount of vinegar in your bottle. If any residual amount of vinegar is left at all after the rinsing, it will not be harmful and with a few uses any smell or taste should disappear.

You can also use a small amount of bleach instead of vinegar to kill mold.

Vinegar and baking soda are a great option for washing your thermos if it has been left for a while or is building up mildew or  residue from coffee, drink mixes, etc.

Vinegar kills the bacteria and baking soda acts as a detergent and deodorizer, breaking up any residue and getting rid of any remaining odors. 

Washing Your Thermos With Boiling Water

Simply fill your thermos with boiling water and let it sit overnight. The extreme temperature will kill the bacteria.

If the inside of your thermos is made of stainless steel, ceramic, or heat-tempered glass, you can use boiling water to clean the bottle.

Washing Your Thermos With Cleaning Tablets

Another way to wash your thermos is by using cleaning tablets specifically designed for the purpose.

Just fill your thermos with warm water and drop the tablets in.

Wait for 15 to 30 minutes as the solution cleans your thermos, then pour it out and rise with warm water.

Several different companies make these tablets, but they all tend to use natural ingredients such as baking soda, hydrogen peroxide, etc.

But I personally like to use the bottle bright tablets from Amazon as they are fairly affordable and have proven to be effective.