What Type of Water Do You Use in a Humidifier?

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Dry winter air brings a whole slew of problems. Your skin cracks, lips prune, and nose gets stuffy. Even worse is when these problems are caused by the air inside your own home.

Using a humidifier in your home can prevent these problems. It will help bring the moisture up to a comfortable level inside your home. 

But there can be some downsides to using a humidifier. Using a humidifier incorrectly can cause increased maintenance costs. It can even reduce the air quality inside your home.

To use your humidifier correctly, the first thing you’ll need to know is what type of water to use in your humidifier.

Why you should use distilled water in your humidifier

Distilled water is the best type of water to use in a humidifier. It has been treated to remove minerals, bacteria, and other particles that can damage your humidifier.

Distilled water is made by boiling water. As the water evaporates into steam, it leaves behind dissolved minerals and other particles. Next, the steam cools, condenses back into water, and is collected. The collected condensate is distilled water.

Distilled water is preferred in your humidifier because of a few reasons:

  • Using distilled water keeps your humidifier clean. Distilled water has been treated to remove dissolved solids. Minerals such as calcium, sodium, and magnesium are present in tap water and will dirty up your humidifier.

  • Using distilled water helps prevent mold growth. Distilled water is much less likely to have mold spores in it. Using distilled water in your humidifier reduces the risk of a mold colony forming inside the humidifier’s tank.

  • Using distilled water improves air quality in your home. Distilled water eliminates the white “humidifier dust” that humidifiers make. Humidifier dust comes from dissolved minerals inside the water that you use in the humidifier. Since distilled water has been treated to remove those minerals, it will eliminate the presence of humidifier dust in your home.

Can you use tap water in a humidifier?

Using tap water in a humidifier is not recommended. Tap water typically contains dissolved minerals and solids that can damage your humidifier. Using tap water will cause crusty scale deposits to form on the interior of your humidifier.

If mineral build-ups weren’t bad enough, microorganisms such as mold and bacteria thrive in scaly environments. The growth of microorganisms will be kickstarted by scale build-ups.

Using tap water in your humidifier will cause a reduction in air quality as well. White “humidifier dust” may appear on the surfaces inside your home. This dust is caused by the minerals inside tap water.

In this case, you’ll need to clean your humidifier frequently. Expect to clean or change your humidifier’s filter quite often, and clean the interior of mineral build-ups.

If you decide to use tap water in your humidifier, an option is to use a demineralization cartridge. A demineralization cartridge will remove minerals from tap water. This will help keep your humidifier clean and your home free of white dust. 

Can you use bottled water in a humidifier?

Using bottled water in a humidifier is not recommended for the same reasons as tap water. While bottled water is filtered to remove particles, it still contains dissolved minerals.

Even though many bottled water manufacturers claim that their water comes from a natural spring, it is not completely pure. Natural sources of water contain contaminants.

But don’t let that worry you too much. If you have nothing else to use, then bottled water is okay for a little while. You won’t notice any immediate effects and it’s unlikely to damage your humidifier if you only use it for a day or two.

If you use bottled water in your humidifier, be sure to switch back to using distilled water as soon as you can. If you don’t, your humidifier will get dirty from scale build-up.

Can you use filtered water in a humidifier?

Using filtered water in your humidifier is not recommended since it is not able to remove most dissolved minerals.

While using a filter is definitely a step in the right direction, it is not able to completely treat tap water for use in a humidifier. Water filters also don’t help much in removing microscopic organisms such as viruses.

Can you use boiled water in a humidifier?

Using boiled water in your humidifier is not recommended. While boiling water will kill bacteria and viruses, it doesn’t remove dissolved minerals.

In fact, boiling water will increase the mineral content of the water. As steam evaporates from boiling water, the mineral concentration increases inside the pot of boiling water.

Even though distilled water is made from boiling water, distilled water and boiled water are two completely different things. Distilled water is made from collecting the steam vapor from boiled water. Boiled water is not made from steam vapor, rather it just heated and collected amongst itself.

One benefit of using boiled water over normal tap water is that it will have a lower chance of mold forming. Since boiling water neutralizes mold spores, you’ll have less trouble with mold and slime.

If you decide to use boiled water in your humidifier, be sure that it cools down before you use it. Putting boiling water in a humidifier will damage it. After boiling water, let it cool to room temperature before putting it in your humidifier.

Should you put hot or cold water in a humidifier?

The short answer… neither! Using excessively hot or cold water in a humidifier is not ideal. Generally, room temperature water is almost always desired for the following reasons:

  • Hot water from your tap is likely to contain more minerals than room temperature water. This is because solids tend to dissolve in hot water. As the hot water flows through your pipes, it will pick up minerals and build-up from the inside of your pipes.

    Using hot water, dissolved minerals will build-up inside your humidifier – even more so than just using room temperature tap water.

    Additionally, using excessively hot water can decrease the lifespan of your humidifier. As the hot water flows through your humidifier, it heats up the mechanical and electrical components. This can cause increased wear and possible damage.

    If mineral build-up and decreased lifespan weren’t enough, you’ll need to worry about bacteria and mold build-up as well. Hot water provides a cozy environment for organic lifeforms to grow inside your humidifier.

  • Cold water will make your humidifier work harder to humidify a room, especially if it’s a steam or warm-mist humidifier. It will also make these types of humidifiers less effective since they need to heat up water to work properly.

There may be some instances when using hot water in your humidifier is perfectly fine. Be sure to consult the owner’s manual for your particular humidifier. Some humidifiers recommend using hot water for increased evaporation rates.

In this case, using hot water would be perfectly fine. Just remember to keep an eye out for mineral and mold build-ups and remember to change the filter regularly!

Hi, my name is Trey Lewis and I’m the founder and chief editor at HVAC Training Shop. My goal for this website is to help homeowners troubleshoot and maintain their home’s HVAC systems. Whether it’s changing an air filter, troubleshooting a blower motor, or just buying a new humidifier, I want to make sure that you’re covered.

6 thoughts on “What Type of Water Do You Use in a Humidifier?”

    • Hi Linda,

      No, you should not use the water from a furnace in a humidifier. Furnace condensate is acidic and has traces of dissolved solids in it.


    • Hi Rachel,

      Filtering & boiling water does not remove most dissolved solids, so I don’t recommend using it in your humidifier. Depending on how “hard” your water is, you will eventually get scale build-up in your humidifier. However, if you’re only using it for a short period of time, then it should be okay.

      In any case, distilled water is best for your humidifier.



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