Can You Put Thermos Flasks in the Dishwasher

When it comes to cleaning our kitchenware, the dishwasher is often our go-to appliance. It’s quick, convenient, and saves us the hassle of handwashing dishes. But what about thermos flasks? These insulated containers are beloved for keeping our beverages hot or cold for extended periods, but can they withstand the dishwasher’s cleaning power without compromising their functionality? In this article, we will delve into this common household query and provide you with the answers you need to maintain your thermos flasks effectively.

The Construction of Thermos Flasks

Before we dive into the dishwasher debate, let’s understand the construction of thermos flasks. These containers typically consist of several layers to ensure their insulation properties:

1. Outer Shell

  • The outer shell is often made of stainless steel or plastic and serves as the flask’s protective layer.

2. Vacuum Insulation

  • Beneath the outer shell, a vacuum layer is present. This vacuum is crucial in preventing heat transfer between the flask’s contents and the external environment.

3. Inner Liner

  • The inner liner is usually made of glass or stainless steel. It holds the beverage and helps maintain its temperature.

The Dishwasher Dilemma

Now that we have a basic understanding of thermos flask construction, let’s address the question at hand: can you put thermos flasks in the dishwasher?

1. Outer Shell

  • The outer shell, often composed of stainless steel or plastic, can typically withstand dishwasher cleaning. However, prolonged exposure to high heat and strong detergents may affect the appearance of the flask over time. It’s advisable to check the manufacturer’s instructions for specific care recommendations.

2. Vacuum Insulation

  • The vacuum insulation is the heart of the thermos flask’s ability to keep beverages hot or cold. Unfortunately, exposing it to the high temperatures of a dishwasher can compromise its vacuum seal. This can result in a loss of insulation properties, rendering the flask less effective.

3. Inner Liner

  • The inner liner, made of glass or stainless steel, is sensitive to extreme temperature changes. Dishwasher cycles can subject it to rapid temperature fluctuations, increasing the risk of cracks or damage. Handwashing is the safer choice to preserve the integrity of the inner liner.

The Best Way to Clean Your Thermos Flask

Given the potential risks associated with dishwasher use, it’s recommended to clean your thermos flask manually. Here’s a simple step-by-step guide:

1. Disassemble

  • If your thermos flask has removable parts, such as a cap or a rubber seal, remove them for thorough cleaning.

2. Gentle Cleaning

  • Use a bottle brush or a soft sponge along with mild detergent to clean the interior. Avoid abrasive scrubbers that could damage the inner liner.

3. Rinse Thoroughly

  • Ensure all detergent residue is rinsed away with warm water. Rinse multiple times to be certain.

4. Air Dry

  • Leave the thermos flask to air dry with the cap off to prevent moisture buildup.

5. Reassemble

  • Once completely dry, reassemble your thermos flask, and it will be ready for your next adventure.


In conclusion, while it may be tempting to toss your thermos flask into the dishwasher for a quick clean, it’s not the best practice. The dishwasher’s high temperatures and strong detergents can compromise the insulation properties and structural integrity of the flask. To ensure your thermos flask continues to keep your beverages hot or cold effectively, opt for gentle handwashing instead.

Frequently Asked Questions (FAQs)

  1. Can I put the cap of my thermos flask in the dishwasher?
    • It’s generally safe to put the cap in the dishwasher if it’s dishwasher-safe. Check the manufacturer’s guidelines to be sure.
  2. What should I do if my thermos flask develops a strange odor?
    • Soak it in a mixture of warm water and baking soda for a few hours, then wash it thoroughly. This should help remove any odors.
  3. Can I use bleach to clean my thermos flask?
    • It’s not recommended as bleach can be harsh on the materials of the flask and may leave a residual taste or odor.
  4. How often should I clean my thermos flask?
    • Ideally, you should clean it after each use to prevent the buildup of odors and residue.
  5. Can I use my thermos flask for both hot and cold beverages?
    • Yes, most thermos flasks are designed to keep both hot and cold beverages at their desired temperatures. Just be sure to clean it thoroughly between uses to avoid any lingering flavors.
Click to rate this post!
[Total: 0 Average: 0]
Spread the love