How To Properly Clean a Thermos Lid (Instructions)

I use my thermos for both drinks and food. Sometimes I fill it with coffee, sometimes soup and sometimes water or smoothies. But this means it can get dirty really quickly, especially in the ridges and seals on the lid.

If you don't clean it properly (and most people don't) it can collect mold so knowing how to properly clean your thermos lid is really important.

To properly clean a thermos lid, you will need to take apart all the pieces that make up the lid. Soak the pieces of the lid in warm soapy water for 10 minutes. Rinse and wash the lid with a solution of baking soda and white distilled vinegar to get rid of stubborn stains. 

Mold and bacteria love dark, damp places, and unfortunately, the ridges and grooves of your thermos lid are the ideal breeding ground for them. 

Knowing how to clean a thermos lid is so important because black mold is very dangerous if ingested, and a dirty lid can make your contents smell bad.  

What You Will Need To Get Started 

Cleaning a thermos lid can be done quite easily using the things you already have lying around at home. 

Cleaners you will need: 

  • Dish soap. Any brand will work 
  • Baking soda 
  • Lemon juice (optional)
  • White distilled vinegar 
  • Home bleach 

As you can see, there’s no need to go out and spend money on fancy cleaners when you can use these common household items. 

Tools you will need to clean with:

  • Dish sponge 
  • Bottle or spout brush (optional) 
  • Q-tips (optional)
  • Cotton swabs (optional)
  • Toothbrush (optional)
  • Pipe cleaner (optional)

These cleaning tools can be used for those hard-to-reach places in the thermos lid. 

How To Properly Clean a Thermos Lid

Here’s how to properly clean your thermos lid. 

Step 1: Disassemble The Lid 

To properly clean, you will need to take apart all parts of your thermos lid.

There are a few common styles of lids found on your thermos. There's a regular twist top lid (which is the easiest to clean), a push button lid or a fastener ring.

How To Disassemble Regular Thermos Lid:

If you have one of the large Thermoses with a regular lid that twists on these are simple to disassemble and clean.

  • Unscrew the lid and take it off the bottle
  • Remove rubber gasket with your finger

How To Disassemble a Push Button Thermos Lid

Disassembling a push button thermos lid can be tricky and involves quite a few steps. Below is a video showing exactly how to do it:

How To Disassemble Twist Top Thermos Tumbler Lid

There are 2 different ways to disassemble your Thermos twist top tumbler lid. This requires a fair few steps so I've included the partial and full breakdown videos below:

Partial Breakdown:

Full Breakdown:

When you have taken apart your thermos lid be sure not to lose any of the lid components. 

Step 2: Soak The Lid 

The first part of cleaning the lid is to let it just soak in hot water with dish soap for 10 minutes. Any dishwashing soap will work for this. 

Sometimes beverages like coffee with milk, if left in a thermos or wasn’t washed properly after use, can start to smell like sour milk, which can make drinking from your thermos rather unpleasant. 

To help with the smell, you can soak the lid in a baking soda, white distilled vinegar, and lemon juice solution. Use one teaspoon of baking soda, ½ cup of vinegar, and one teaspoon of lemon juice. The juice is optional. 

If you are going to be using vinegar in your cleaning solution, do not use brown vinegar as the smell is very strong, and your drinks will constantly smell of vinegar. Trust me, just avoid it! 

Once the 10 minutes is up, you can clean the lid with a gentle dishwashing sponge and rinse the soap off.

Step 3: Scrub The Lid 

If your thermos is particularly dirty or if you have black mold growing, you will need to scrub the lid thoroughly. 

First, you will need to make another baking soda and vinegar cleaning solution. You will notice a chemical reaction occur when you mix the ingredient, this is totally normal. 

Using your choice of cleaning accessories like a brush or q-tip, start scrubbing all the components of the thermos lid, paying extra attention to under the valve and in the ridges of the lid. Scrub until the lid is clean. 

I personally like to use this bottle brush cleaning kit from Amazon as it's affordable and features a bottle brush for easily cleaning inside my thermos as well as smaller brushes which allow me to get into all the gaskets and little crevices to clean them well.

3-in-1 Stainless Steel Water Bottle Brush Set
$19.99 $15.95

Three tools in one. Includes a long bottle brush, straw brush and detail cleaner (great for cleaning inside lid gaskets). Comes with organizer ring and storage hook,

Buy Now at Amazon
02/02/2023 09:28 am GMT

Sometimes mold can be stubborn, so you may need to bring out the household bleach and use one teaspoon of bleach with hot water. Let the lid soak for 5 minutes before scrubbing the mold off. 

This is only recommended for very stubborn mold and not just general cleaning of the thermos lid. 

Step 4: Rinse and Reassemble The Lid 

When you are happy with the cleanliness of your thermos lid, you can rinse off the cleaning mixture. I suggest doing this twice. There is nothing worse than soapy coffee or vinegar in your coffee.

Dry all the parts of the lid well before reassembling the lid, and when you are doing this, you simply need to work backward from when you removed the lid.

Everything should slot easily back into place. 

Now you can use your thermos without worrying about any nasty germs or smells! 

What Are The Best Ways To Clean Thermos Gaskets?

The gasket on the Thermos lid is the biggest culprit when it comes to horrible odors in your thermos. Luckily cleaning the gasket is really simple.

First pull the rubber gasket off the lid with your fingers. It comes off pretty effortlessly.

If there is mold or gunk on there then give it a bit of a rinse and scrub before soaking the gasket in vinegar to kill any mold.

I like to soak my gasket in 1-2 cups of white vinegar and scrub the grooves and nooks with a small brush.

Be sure to rinse thoroughly to remove any leftover vinegar. 

You can use a baking soda and water paste which you put on the gasket and can scrub the gasket gently. Rinse well when done.

Should I Clean My Thermos Lid Or Just Replace It?

You can pretty much always salvage a thermos lid and shouldn't throw it out. However, sometimes you may need to replace it.

Giving your thermos lid a deep clean can do wonders, it will look brand new and it is pretty easy to clean. Even for lazy people like me.

However, if the lid is still leaking this might mean a broken gasket which you’re better off just replacing then trying to fix it. 

Where To Buy Replacement Thermos Lids

Brands like YETI, Hydro Flask and Camelbak will have replacement lids available to purchase from their websites.

Amazon also sells replacement lids for many of the popular thermos brands. Make sure you get one with a good rating and some of them have terrible rating and seem really poor quality.

This replacement lid at Amazon for a classic 1.1-quart or 2-quart thermos seems like a good option.