How Often Should I Change the Water in a Water-Based Air Purifier?

If you’ve owned a water-based air purifier for any amount of time, then odds are that you’ve wondered how often you should change the water in it.

You’ve probably wondered why it’s important, if it helps, why the water level in your air purifier’s basin goes down, and so many other things as well.

And that’s what I’ll tell you about in this article! But, first thing’s first, let me answer your main question:

You should change the water in your water-based air purifier once every one to two days. When doing so, be sure to rinse the fan and basin. Be sure to change your water when the basin’s level drops to the minimum fill line as well.

Why Do I Need to Change the Water in My Water-Based Air Purifier so Often?

It is recommended that you change the water in your air purifier every one to two days because the water needs to be as clean as possible in order to continue cleaning the air. Many people notice that the water in their water air purifiers gets dirty and/or cloudy when they don’t change their water as often.

But, it isn’t the end of the world if you don’t change it as often. Changing the water once or twice a week shouldn’t be the end of the world, but it will impact the quality of air that’s being cleaned, it may mean your air purifier will develop a smell, and you will have to clean your water-based air purifier more often.

In addition to all of that, there is the ever-present risk of mold growth in your air purifier. Since it’s a wet area, mold might want to grow there. The best way to ensure that doesn’t happen is to change your water often and to wash your water-based air revitalize from time to time. In this article I wrote, I show you (with pictures) how to clean your water-based air purifier and I recommend that you do so every 6 to 8 months. Cleaning your air purifier more often just means you’ve got cleaner air (and a cleaner machine), so you can do that as well.

Beyond the mold threat, there is also the issue of your air purifier potentially running dry or, at the minimum, its water level dropping below the minimum fill line. There are a few reasons why you don’t want to let that happen. For starters, I find that the air coming out of my air purifier is cleaner when it’s full. In addition to that, the air purifier can be harder to clean when the water level drops too low, since the junk that it collected will dry and cake onto your machine. Keeping your air purifier full will get you cleaner air and it will save you time when you have to clean it.

Why Does the Water Level in My Water Air Purifier Drop?

Believe it or not, the water level in your water-based air purifier can drop as you run it! Some people may have the water run out in as little as a day while others might have that process take a whole week.

But… Why does it happen?

The water level in water-based air purifiers drops while they are in operation due to evaporation, this is why air revitalizers like these claim they serve as “light humidifiers” and other similar claims. Water levels are more likely to drop at a rapid rate in hot and dry climates.

I’ve found that the amount of humidity that air revitalizers add to the room is very light, which is a nice change from the muggy hot air that you get from some humidifiers on the market (although ultrasonic humidifiers don’t add any heat). Because of the comfortable amount of humidity water-based air cleaners add to the air, I can see why they’re also called revitalizers. They really revitalize the air.

But, that comes at a cost: you’ll have to refill the basin of water more than you might want to. For me, I have to top off my air purifier every day (sometimes multiple times a day) because the water is sucked out so fast. In fact, in the time I’ve been writing this article, the water level in my air purifier’s basin has gone down halfway!

But, the water level dropping in your water-based air purifier is nothing to worry about, if anything, it’s a good indicator of your home’s air quality! If it drops really fast, then you might want to buy a humidifier for your home to increase its humidity. If you’d like to learn a little more about that, check out this article I wrote: How Do I Know if I Need a Dehumidifier or a Humidifier? | What’s the Right Humidity for My Home?

When Should I Change the Water in My Water-Based Air Purifier?

You should change the water in your air purifier once every day or two, or whenever it appears to be dirty. If the water begins to smell bad, that’s another indicator that it’s time to change the water (and clean your air purifier).

My air purifier gets these weird clear floating globs in it when it runs for more than a day, but they’re translucent and you can’t even see them if you don’t turn off the air purifier (all the waves make it impossible to see them). But, when you turn it off and jiggle it around, you can see the globs. They look a little bit like squished water babies.

Now, I’m no scientist, but I’m willing to bet that those things aren’t things that I want to be breathing!

So, I make sure that I change the water in my air purifier’s basin often. If I don’t, then those glob things start multiplying and that can’t be good for the air purifier’s cleaning ability.

And, as I’m sure you know, dirty water that you can see is all sorts of nasty is a pretty good indicator that it is time to change the water in your air purifier as well. No, you probably won’t get too dirty of water if you change it every day or two, but it is possible. Something that I got to add here is that when you let the water get really dirty, just rinsing off and out the water-based air purifier might not be enough to clean it out. You’ll probably have to do a deeper cleaning, and that’s no fun. So, keep up on things.

What About Essential Oils in My Water-Based Air Purifier?

Okay here’s something I think is really cool about water-based air purifiers: you can put essential oils in them.

But, that does come with a little bit of a drawback. Namely, your water basin seems to get dirtier faster.

I attribute that to the fact that oils tend to do that in general, but I’ll add that fragrances that aren’t oil-based tend to dirty the water as well. I know that might sound like a bad thing, but I think it’s actually more of a good one.


Well, you bought an air purifier, after all. If the water is getting dirty, then it’s doing its job! I’ll probably do a science experiment in the future to test and see if the air is actually getting cleaner, but I wouldn’t be at all surprised if it was. At the end of the day, though, it’s up to you to decide what you want out of your water-based air purifier. I think they’re really cool, and I think they work great too.

But, they’ve got their pros and cons, which you can check out in this article I wrote: What is a Water Based Air Purifier? | The Pros & Cons of Water Air Revitalizers. One big con to water-based air revitalizers is the fact that they don’t quite measure up to the nicer air purifiers on the block, air purifiers with HEPA filters and electrostatic plates work a lot better at moving the air and removing particles. Sure, water-based air purifiers work pretty well, but the costlier ones tend to do a better job (but not always).

If you’re in the market for more water-based air purifiers, here’s a list of the best ones I’ve seen to date: What Is the Best Air Purifier That I Can Buy? | Water Based Air Purifier Buying Guide. If you’re in the mood to check out air purifiers with HEPA filters which will clean the air better, then here’s another list where I share my all-time favorite air purifier recommendations: Air Purifier Essentials Top Picks: Best HEPA Air Purifiers on the Market

Jonathon Silva

Jonathan Silva is our longtime Air Purifier Essentials author. He has been writing on air purification technologies for his entire professional career.

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