How to Clean a Flask The Smart Way In 5 Easy Steps

Reusable flasks and bottles are economical and better for the environment. The one drawback, however, is cleaning and sanitizing them. While some flasks and bottles can be run through the dishwasher, many can’t. (And even when they are dishwasher-safe, the container’s narrow shape makes it unlikely that it gets a thorough cleaning.)

To learn how to clean a flask, read on.

How to Clean a Flask Bottle

Stainless steel flasks are among the most popular water bottles these days. They’re incredibly durable, usually don’t have an aftertaste, and are available in a variety of colors.

If you have a stainless steel flask with a powder-coated color finish, never put it in the dishwasher. The grit of the dishwasher detergent will wear away the finish. Instead, follow these cleaning instructions:

1. Pour a little dish soap into the flask, then fill it most of the way with hot water from the tap.

2. Use a designated bottle brush to scrub the inside of the bottle. (For sanitary reasons, you’ll want to use this brush only for cleaning your bottle.)

3. Pour out the soapy water, then soap up and wash the outside. (Be extra gentle if the bottle has a powder-coated finish and don’t use abrasive sponges or scrubbers on the outside.) Wash the bottle’s cap or lid with warm, soapy water too.

4. Rinse the inside and outside of the bottle several times with warm water until there are no more soap bubbles or soapy residue. Do the same with the bottle’s cap.

5. Dry the bottle and cap upside down in a drying rack.

How to Clean an Alcohol Flask

Another type of flask that finds its way into backpacks or camping gear is a metal alcohol flask. With a tiny opening, these containers can be especially tricky to clean. The following cleaning instructions are for stainless steel flasks only. If your flask is made from pewter or another material, it will require extra care.

1. Empty the contents from the flask. Then fill and rinse the flask several times with warm water.

2. Add a couple drops of dish soap to the flask and fill it with warm water. Let it sit for 5 to 10 minutes. (To clean and deodorize, you can also fill the flask with equal parts water and white vinegar and allow this mixture to sit.)

3. Pour out the soapy water or vinegar mixture. Then rinse the flask several times with water until all soapy residue is gone.

4. Dry the flask upside down in a drying rack and let it air out before refilling.

Recommended Brushes

If you frequently wash flasks and water bottles, you may want to have some specialty brushes on hand to make the job easier.

Silicone brushes are great because unlike some bristle brushes, they won’t scratch surfaces. This silicone brush has a long handle and comes with a wall mount so you can hang it up when it’s not being used. The brush is also dishwasher-safe so you can keep it clean and germ-free.

This brush set includes 3 types of brushes: a water bottle brush, a straw brush, and a small “detail” brush you can use to clean lids.

In the market for a new flask? Check out our post on the best insulated bottles, flasks, and containers.