Does Distilled Water Go Bad?

No matter if you’re drinking distilled water on a daily basis, or only buying it every once in a while for your steam iron, at some point you probably started thinking: does distilled water go bad?

If you’re distilling water at home using a steam distiller, on more than one occasion, you probably considered storing some water in case of an emergency. And you probably weren’t sure how to go about that.

Or maybe you’re using distilled water only occasionally to refill the humidifier or any other home appliance that requires it. And after a few months, you started to wonder if that half-full container of store-bought distilled water ever goes bad. It’s not that anyone will ever drink that water, but you care about your appliances and want to keep them in top shape.

Either way, if you have any questions or doubts about storage, shelf life, and “going bad” of distilled water, this article is for you.

Water bottles
Image used under Creative Commons from Nathalie

But before we begin, please note that there is a lot of controversies when it comes to whether humans should drink distilled water or not. In this article, I won’t go into any details on that because that’s not relevant to the topic. In other words, it’s up to you whether your drink distilled water or not. And if you’re only using it for home appliances, you will find some useful information in this article too.

How to Store Distilled Water

The basic storage guidelines for distilled water are very similar to “plain” water. Keep the unopened bottle or container in a cool place away from sunlight. Once you open it, remember to always keep the container sealed tightly when not in use.

Storing Distilled Water for Home Appliances

Let’s talk about storing water for purposes other than drinking. If that’s the case, keep the product away from solvents and chemicals such as gasoline, paint thinners, household cleaners, and dry cleaning chemicals. Just as an extra precaution.

If you’re storing the distilled water long term, a high-density polyethylene container is the best choice. Of course, there’s no point in buying one if you’re only storing a few ounces at a time for ironing.

Storing Distilled Water for Drinking

If you’re distilling water at home for drinking purposes, a glass container for water seems to be the best idea, as many home water distillers come with a glass tank. But a plastic BPA-free food-grade bottle will be just fine too.

If you’d like to store some water in case of an emergency, one big or a couple of smaller containers will do the job. Again, make sure they’re made for contact with food. The theory is the distilled water will stay safe indefinitely, provided that it’s sealed tightly, but I’d change that water every few months nevertheless. Especially if it’s in a plastic container.

Water
Image used under Creative Commons from Brian Smithson

How Long Does Distilled Water Last

Like plain water, store-bought distilled water lasts pretty much indefinitely when stored properly.

When it comes to distilled or purified water meant for home appliances, it can easily last a few years when unopened, and another year or two after opening if you take good care of it. There’s no point in getting stressed that the water for your steam iron will somehow “spoil” and damage the appliance.

If you’re distilling water at home, its quality is best for probably a week or so. After that time, it might start to smell somewhat stale. Of course, it’s still safe to drink and all, but you might want to discard it and go with a fresh batch.

 Pantry
Bottled distilled water (unopened)5+ years
Bottled distilled water (opened, for appliance use)1+ years
Bottled distilled water (opened, for drinking)4 – 7 days
Home-distilled water4 – 7 days

Please note the periods above are estimates and for the best quality.

(credit: Cory Doctorow)

How To Tell If Distilled Water Has Gone Bad

In short, if distilled water was stored properly, it should be perfectly fine, both for drinking purposes and use in home appliances. But as I already mentioned, after a few days of opening the bottle or distilling the water, it might start to “smell” ever so slightly, and don’t taste well because of that. That’s often more of an issue with the container that the water itself.

But if you notice that the smell of the distilled water has changed significantly, or find that any impurities got into the container, discard the water. Same thing if it tastes off. If it’s water for appliance use and looks and smells like usual, feel free to use it.