Is A Thermos Dishwasher Safe?

A thermos is excellent for keeping your favorite food and drinks hot or cold all day while you’re on the go. If you use your thermos every day, you will experience some wear and tear, getting dirty, just like everything else in your kitchen! Is a thermos dishwasher safe?

Some thermoses, such as stainless steel, are dishwasher safe. However, it is advised that you handwash them, as the harsh detergent and heat could damage and shorten the lifespan of its insulation. Usually, a thermos’s lid is considered dishwasher safe when placed on the top rack.

If you own a dishwasher, throwing your thermos in with the rest of your dishes might be very tempting. However, continue reading with us as we explain why you should hold off on putting your thermos in your dishwasher and what could happen if you do!

Thermoses That Are Dishwasher Safe

There are some rules and regulations regarding placing dishwasher-safe thermoses in the dishwasher. Stainless steel insulated thermoses are considered dishwasher safe, but only if set on your dishwasher’s top rack.

Instead, it is also advised to clean them by hand, as the dishwasher could potentially cause them harm. However, if you are still willing to wash your favorite stainless steel thermos in your dishwasher, you should keep it in the top rack section.

Keeping your thermos in the top rack of your dishwasher will not cause your thermos any harm, and it will be returned squeaky clean and the way you remember it!

Never place your thermos at the bottom rack of your dishwasher, as it will most likely become severely damaged and lose its durability.

It could also cause harm to the vacuum seal of your thermos, which means it will not insulate properly, causing your drinks or food to become hot or cold in a short time.

Two other things in your dishwasher that could contribute to shortening the lifespan of your thermos are the heat and the detergent.

This could also cause harm to your thermos, not causing it to insulate properly. If you want to get the most out of your thermos without it losing its durability and initial beauty, it is suggested that you wash them by hand.

Many brands and manufacturers guarantee that their thermoses are durable enough to place in your dishwasher. The only consideration is that you should keep them in the top rack.

The best thing you could do is, before purchasing a thermos, always keep a close eye on the manual, as you will get a better idea of whether or not it is dishwasher safe and what could potentially happen If they land in the dishwasher.

Thermoses That Are Not Dishwasher Safe

Glassware vacuum insulated thermoses are never dishwasher safe. It is highly advised to wash any glass thermoses by hand if you want them to last to their fullest potential.

Keeping a glassware thermos in the bottom rack of your dishwasher could cause significant damage, such as shattering, due to the heating element attached to your dishwasher’s bottom.

The detergents used in a dishwasher could also cause the glass to become scratched or damaged, making your thermos more prone to leaking.

A Thermos’ Lid Is Always Dishwasher Safe

You may be happy to hear that the lids of thermoses are dishwasher safe, but only when placed on the top section of your dishwasher. A thermos’ lid is made of a mix of rubber and plastic parts that screw together to form a vacuum seal.

However, because of the many different parts, it is mostly advised that you hand wash the lid, but not because the lid may break. Handwashing a thermos’ lid is recommended as it prevents the build-up of mold, which could happen in a dishwasher.

Furthermore, you would also want to pay close attention to the rubber gasket part of the lid, as this is the primary place mold could build up.

This part should be removed after each use and cleaned correctly; this is not something an electrical washing machine can do better than your own hands!

You can remove the rubber gasket and give it a hard scrub with a sponge or brush to get rid of any potential mold.

Leave it to air dry separately before putting it back on your thermos’ lid. If you do not make this a regular part of your thermos cleaning routine, you may end up consuming mold spores, potentially making you sick. 

Consequences Of Placing A Thermos In Your Dishwasher

You may be wondering what could happen if you go ahead and put your thermos in your dishwasher. If you place your thermos on the dishwasher’s top rack, you can rest assured that it will be fine and come out squeaky clean for your next use.

However, it would be best if you kept in mind that you run the risk of causing severe damage to the vacuum seal, causing your thermos not to insulate properly.

The harsh heating element of a dishwasher is located at the bottom, which could instantly shatter a glass vacuum insulated thermos and break the vacuum seal entirely on a stainless steel thermos.

However, there have been multiple reports of people who never knew that they should not place their thermos on the bottom rack of their dishwasher, and they have been happy with the results. Their thermos ended up squeaky clean, which you would expect from any dishwasher, without causing any damage to their thermos or its insulation.


If you’re wondering whether or not your thermos is dishwasher safe, it might be a good idea to err on the safe side. Handwashing your thermos isn’t usually a difficult or time-consuming process; it exposes your thermos to less heat, which will be less likely to cause issues.

Dishwashers also have the potential to discolor thermoses. The best way to take care and clean your thermos would be to hold on to the user’s manual! After all, you don’t want to sip on your hot drink only to spill it on yourself due to a break in the vacuum seal of your thermos!


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