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Does Distilled Water Need To Be Refrigerated Once Opened?

Most distilled water containers have expiration dates, which is not usually seen on other water bottles. I was curious if this meant the shelf life could be extended through refrigeration or if it mattered. I’ve been storing liquids and preserving food for over 50 years, so I thought I’d share what I’ve learned with you.

You do not have to refrigerate an opened container of distilled water, but you must make sure you store it properly. Unlike traditional water containers, distilled water is prone to taking minerals and other materials from the container it is in, so storing it the right way is essential.

Read on to learn more about the topic, as well as tips on how to store distilled water properly.

View From Inside a Fridge of a Man Grabbing Bottled Water

How Do You Store Distilled Water After Opening?

After opening a container of distilled water, there are different ways you can store it. Unfortunately, it might not be safe for drinking or any other function if you do not store it properly. While water itself can last theoretically indefinitely, distilled water needs a bit more attention to the storing process.

There are a few things to keep in mind when choosing how to store distilled water after opening it:

  • How tight the seal is: One of the first things you must make sure of before storing your opened distilled water is that the seal is as tight as possible. As with any other type of water, distilled water picks up odors from other materials it is around. While you should not store it next to odorous cleaning chemicals or the like, if you do, the distilled water might pick up an odd odor.

You also need a tight seal so that bacteria, chemicals, or anything else cannot find its way into the container. If your seal is not tight enough, materials can quickly find their way into the container, contaminating your water or affecting the shelf-life.

  • Where you will store it: Where you store your distilled water is an equally important factor. You can store your distilled water in a refrigerator, but it is not required. Storing it in the fridge like any other water will keep it perfectly safe. As long as it is in a cool, dark place, your distilled water will last as long as it should. 

Keeping distilled water away from sunlight is important, as this might make it easier for bacteria and other materials to find their way into the distilled water container.

  • Type of container you will use to store it: Lastly, you must choose the proper container in which to store your distilled water. If you are storing large amounts for use in home appliances like a CPAP machine or humidifier, you might consider storing your distilled water in a high-density polyethylene container. Since the minerals are taken out of distilled water, storing distilled water in a regular plastic container is not the best idea. 

If you do this, the distilled water can start soaking in chemicals or other harmful materials from the generic plastic.

Related How Long Can You Keep Bottled Water in Your Car?

If you have distilled water for drinking or any other short-term use, you may not need a high-density polyethylene container. For smaller amounts, sealable glass containers will do just fine. In any case, make sure your distilled water is out of contact with direct sunlight, sealed as best as possible, and in a sufficient container void of chemicals that will be attracted to the water.

View From Inside a Fridge of a Man Grabbing Bottled Water

Does Distilled Water Go Bad Once Opened?

If you buy distilled water from a store, the chances are that it has an expiration date on it. At the very least, it might have a label saying something like “best before x.” While this is something to be aware of, it is not drastically important.

Unopened distilled water can last for over two years. Once you open it, however, the shelf-life will not be as long. 

If you have distilled water for drinking, you should not keep it for longer than a few weeks, especially if it is not refrigerated. However, distilled water for use in home appliances can last upwards of a full year after being opened.

It is not that distilled water is deadly to drink after a week or so of being opened, but it will likely taste a bit unusual. If you see algae growing in the container or you notice an odd smell, you should not drink your distilled water. This is probably a result of improper storage, and even for home appliances, you may not want to use water with a green tint to it.

Can Bacteria Grow In Distilled Water?

Bacteria can grow in distilled water. This is why storing it the right way is essential to making it last. As said before, if you store your distilled water in a plastic container, there is a high likelihood that the water will take in chemicals from the plastic quickly.

As with any other type of water, leaving your distilled water in contact with the sun will speed up the process of allowing bacteria to grow. You also need to consider whether you buy your distilled water or distill it yourself at home. 

If you distill it yourself, you may not have the industrial-grade equipment to make it last as long as store-bought distilled water. In this case, bacteria might grow in it more quickly.

Laboratory Test Bottle of Distilled Water

Why Does Distilled Water Have An Expiration Date?

Distilled water has an expiration date because there is a timeframe in which it is in its purest form. Over time – and as a result of improper storage – distilled water can attract minerals, chemicals, and other materials from both its container and its surroundings. It only stays pure for so long, so companies label it with an expiration date.

If you store your distilled water properly, it can last for much longer than its expiration date might say. And as mentioned earlier, there is a chance it is not an expiration date but rather a ‘best by’ date. If you follow the tips above, you can make your distilled water last for as long as possible.

Related How Much Emergency Water Should I Stockpile and Store Per Person?

Can You Use Expired Distilled Water In A CPAP Machine?

As long as it has been stored properly and you do not detect any signs of contamination, distilled water past its expiration date can work just fine in a CPAP machine. 

Keep in mind, however, that it is easy to notice if your distilled water has gone bad. If it has a blue-green hue to it, if it smells unusual, or if you notice a weird taste – which may not apply for home appliance use, you should not use it.

Can You Use Expired Distilled Water In A Humidifier?

The same rules as above apply to using expired distilled water in a humidifier. You use a humidifier to add moisture to the air for better breathability. Well, this process will do you no good if you are using contaminated water. But, as you already know, not all expired distilled water is contaminated.


Distilled water does not need to be refrigerated once opened, but it is certainly not detrimental to do so. However, you have to make sure that you are storing your distilled water properly. Failure to store it correctly will result in distilled water that becomes contaminated and goes bad more quickly.

I hope this article has been helpful. Thanks for reading!

For more, don’t miss How to Re-Mineralize Distilled Water.