How to wash a hydro flask insulated thermos

How to easily wash your Hydro Flask and other insulated water bottles?

You’ve just got your new Hydro Flask and used it for the first time! But once you’ve gone past storing water in it, you probably want to give it a good clean before its next use.

This weird world of Hydro Flasks has all kinds of strange rules, so you don’t do damage. That’s why I’m going over how to wash your hydro flask.

Cleaning a Hydro Flask is necessary to maintain its performance and keep bacterial growth at bay. By cleaning your flask regularly, you can extend the life of the container by reducing the number of bacteria that accumulates.

Regular cleaning will also remove any sediment or build-up that may have formed over time. With proper care, you can protect your investment and have a great bottle for your favorite beverages.

Don’t be intimidated. In most cases, it’s a pretty simple process that only takes a few minutes.

I personally love using my Hydro Flasks and other reusable water bottles over a single-use bottle any day. It keeps my water ice-cold on the hottest hikes! But after some time on the trail, it’s definitely in need of deep cleaning every now and then.

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What do you need to wash your Hydro Flask?

Chances are you have plenty of these products lying around your house. If you don’t they are easy to pick up at any home store.

  • Dish Soap
  • Bottle Brush
  • Drying Rack
  • Distilled White Vinegar
  • Baking Soda
How to wash a hydro flask insulated thermos

How to wash your Hydro Flask?


Start by rinsing out the container of the bottle with warm to hot water. Hot water is preferred because it dissolves any dried bits on the inside and outside of the flask.

Depending on what’s inside, you may need to let whatever is inside soak for a few minutes until it breaks down and is relatively clean of debris.

Soak with Soapy Water

The next step is to soak the bottle in warm soapy water. You can do this by filling up the sink or filling up the bottle.

I’m a bit of a conservationist when it comes to washing dishes, and prefer to add hot water to the water bottle with a small amount of dishwashing liquid.

After it’s been soaking, give the bottle a scrubbing with a bottle brush. Make sure to get the outer wall on the inside of your bottle with the brush, as well as the bottom of the bottle.

Bottle Brushes are usually found in most stores, if you have trouble finding them, then you can go on Amazon and wait a day before doing it. At least that’s what happened to me.

Finally make sure to wash your Hydro Flask cap and edge, making sure to scrub any place the mouth touches are important.

My favorite bottle brushes and cleaners.
Silicone Bottle Brush with Straw Attachments
Traditional Bottle Brush

Scrubbing a Hydro Flask

Rinse & Dry

Once you have completely scrubbed your bottle give it a good rinse and let it air dry.

I like to have mine upside down on a drying rack, but if you don’t have one, placing it upright will work too. It just takes a little longer.

Did you know you can easily swap out your hydro flask lids?

Depending on the adventure, I swap between a straw flex cap and the traditional lid.

Drying a Hydro Flask

Remove the O-Ring on the cap

The lid is a vital part of maintaining the seal and insulation of the hydro flask water bottle. Most people will take a scrub brush to the exterior of the cap and call it a day.

But the most important part is the rubber O-Ring and it’s where mold often gets trapped. You’ll see this on insulated thermoses everywhere. The Hydro Flask is no different.

The good news is it’s super easy to clean. Taking a butter knife, or a special tool, carefully remove it from the cap. Soak the ring in warm water for a few minutes and remove any debris. In most cases, you can gently rub the gasket with your fingers to clean it.

Then take your bottle brush and detail the area the o-ring was sitting on the cap. This should be done weekly if you use your bottle daily or after each trip if you only use it a few times a month.

O-Rings can be purchased online too if you find it’s damaged. If you forget to replace the rubber gasket o-ring after cleaning it can cause leaks and you’ll lose your vacuum seal.

If your O-Ring is not in good shape, you may need to replace it. You can pick them up on Amazon.
Wide Mouth O-Ring Replacement Set
Coffee Lid O-Ring Replacement Set

Other accessories and caps

If you have specialty accessories, like a hydro flask straw lid, you’ll need another straw brush.

First, make sure to remove the red seal cap connected to the bottom of your cup. Clean all pieces like you would normally, including using the small brush in all spaces in the cap.

Do the same process with the straw, getting out any leftover residue you may have.

Let sit out to dry.

How to get out suborn stains on a Hydro Flask?

Vinegar Soak for Funky Smells

White distilled vinegar is the best way to clean products of bad smells. When it comes to water bottles, if it has the smell of flavored water or the last cold beverage you had, it ruins the whole thing for me. It’s really easy to remove it though.

Using a half cup of vinegar, swirl it around in your bottle touching all affected areas. Let sit for five minutes before rinsing out. Rinse with warm soapy water and let air dry when done.

Baking Soda Paste for Stubborn Stains

Another option for stubborn stains like tea and coffee is to use baking soda with a small amount of warm water. This creates a magical cleaning paste that will work on most surfaces, including inside your bottle.

Start by adding 2-3 tablespoons of baking soda to your bottle. Drop a small amount of warm water inside. Then use your cleaning brush inside the bottle to work out the stains. Rinse the bottle and air dry when done.

Baking Soda in a Hydro Flask for Stubborn Stains

What to avoid when cleaning your Hydro Flask?

Steel Wool

Do not use a wire or steel brush on the exterior powder coat of the stainless steel water bottle. They can scratch the exterior surface and cause damage to the paint.

If you have a difficult stain on the interior, they will work fine. I actually recommend using 0000-grade steel wool to get off hard stains left behind by coffees and teas. This is ultra-fine wool that gives it a good polish.

Use it in combination with a brush on the inside. Once done, pull it out of the bottle. Only use this if the above options don’t work.


Bleach and Stainless Steel do not mix. It can discolor the inside of the Hydro Flask bottle giving it the exact opposite effect you are looking for.

What about Specialty Cleaning Products?

Do you need the buy a natural cleaning tablet? Short Answer No. Your normal dish soap is more than capable of keeping your Hydro Flask Clean.

Are Hydro Flasks Bottles Dishwater Safe?

According to Hydro Flask, all powder-coated bottles are dishwasher safe. Never put the Hydro Flask Coffee Mugs in the Dishwasher.

Exposing the flash to dishwashers’ extremely high temperatures can get so hot it will affect the insulation properties of the bottle. It can also damage the powder coating. You should never use boiling water either.

The same can be said for putting it in the freezer, or even leaving it in your car overnight during the winter if you live in a cold state.

The cap is also not dishwasher safe. According to the hydro flask website, if soaked in water for an extended period of time, it can take on water.

I personally have let both of these happen to my hydro flasks and haven’t had a problem. That doesn’t mean it won’t happen.

Looking for a cheaper ultralight alternative to a Hydro Flask with all the same thermal benefits? Check out the Super Sparrow line. Not only are they less expensive, but their caps and accessories are interchangeable with Hydro Flask. check out my full review: The Super Sparrow Water Bottle Review.
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Tips for storing and washing your Hydro Flask for next time

Store your clean bottle in a cupboard for safekeeping. If the bottle is 100% dry, feel free to reassemble any remaining parts, including the lid, and put it in your favorite cabinet or dry place.

If you are like me and have amassed a collection of lids, straws, and other accessories for your Hydro Flask, store them separately. I like to use a small storage rack for all the lids. This way I can store them and not worry about them being 100% dry.

When I’m ready to go, I grab the correct lid for the correct type of drink and head out.

Buying alternative lids for your Hydro Flask is a big cost saver compared to buying extra bottles. Here are some of my favorites!
Hot Drinks – Coffee Lid
Cold Beverages – I love the straw
Thicker Beverages – A straw or traditional lid works well. Depending on how thick you are talking.

Hydrating on the trail

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