Using RO Water In A Humidifier: Is It The Best Choice


If you live in a place with dry air, a humidifier can be an absolute lifesaver. Essentially, a humidifier… well, makes the air more humid. Additionally, they relieve the symptoms of respiratory conditions, sinuses, nose bleeds, and even dry lips. How does one humidify a humidifier? Can you use just any type of water in one?

RO water should be used in a humidifier occasionally. RO water can contain scale-forming minerals that can damage your humidifier and can also leave fine powdered deposits throughout your house as the mist settles. Distilled water is pure and mineral-free, making it the ideal choice for a humidifier.

Here’s the deal. Your humidifier needs pure water. And when we say ‘pure,’ we mean the purest water you can find. But why is your humidifier so picky about water in the first place? Let’s find out.

Why Does A Humidifier Need Water

You might think this is a no-brainer, but there’s a lot more to it.

Ideally, your home must have 30-50% humidity. Levels below that may result in a sore throat, dry skin, or a bloody nose. Additionally, your sinuses may act up. A humidifier helps keep all this at bay.

A humidifier disperses water vapor into the air to boost your immediate environment’s moisture level. How your humidifier does this depends on the type you have:

  • A central humidifier is a part of your home’s air-conditioning system to humidify the entire house
  •  An impeller humidifier uses a high-spinning disk to disperse water vapor in the room
  •  An ultrasonic humidifier uses fast ultrasonic vibrations to produce a cool mist
  •  A vaporizer boils water, makes steam, and humidifies the room
  • An evaporator makes uses a wet filter or a wick and blows fast air through it, dispersing vapor

For this central function, humidifiers need a regular supply of clean, pure water.

What Water Can I Use?

Regardless of the mechanism, the efficiency of the humidifier largely depends on the water you use.

Tap water is a big NO when it comes to a humidifier, according to the Environmental Protection Agency. Tap water is usually hard – it contains many dissolved minerals and salts. When this mineral-rich vapor is dispersed as a mist, it may settle down to form a cloud of fine white dust around the room, especially on top of furniture and over curtains. These calcium and magnesium deposits are a rich breeding ground for bacteria.

Further, hard tap water also causes a scaly buildup inside the humidifier which exacerbates the problem.

If you don’t clean the buildup often, bacteria, mold, and mites can grow inside. This results in these pesky parasites invading your entire home, causing colds, allergies, and serious health issues.

This is particularly detrimental to children and the elderly and may trigger allergic reactions. Breathing in such microorganisms may cause respiratory illness. 

The same is the case with unfiltered well water. Well water is mostly hard, and may also contain bacteria. Well water from aquifers is rich in minerals, and must not be used in a humidifier without demineralization.

What About Bottled Water?

You may use bottled water occasionally but it is not recommended for long-term use.

Bottled spring water is mineral-rich, and causes a scale buildup over time. This means that bottled spring water, groundwater, and mineral water must not be used.

What About Reverse Osmosis Water?

Reverse osmosis (RO) water may be used occasionally, but this depends on the mineral content of your water.

RO water has fewer minerals than tap water, as larger particles are removed during the filtration process. However, it is still not as pure as distilled water and cannot remove scale-forming minerals such as calcium. Therefore, you may use RO water sometimes, but make sure to be even more diligent about cleaning your humidifier.

As a general rule of thumb, avoid using any mineral-rich water in your humidifier.

The Best Option: Distilled Water

This leaves distilled water.

Distilled water refers to purified water that has no minerals or contaminants. Distilled water is demineralized and deionized, making it perfect for your humidifying device. This is the best type of water for a humidifier as there are no water contaminants or additives to worry about damaging your humidifier or your health.

I highly recommend this Megahome distiller (affiliate link to Amazon). It has a beautiful glass collector and a stainless steel body making it very hygienic and easy to clean.

Click on the image to check it out for yourself on Amazon.

Hot or Cold Water?

Some humidifiers boil water to release a warm mist, while some use fans and wicks to disperse a cool vapor in the room. Regardless of the type you have, do not put hot water in your humidifier. Hot water can damage the internal components of your humidifier.

Cold or room-temp water should be used in a humidifier. Follow your manufacturer’s instructions for optimal results.

Humidifier And Scaling

Using tap water, well water or mineral water can lead to scale buildup in your humidifier’s tank. The calcium and magnesium dissolved in the water form a hard scale on the walls and base of the humidifier’s tank. However, do not lose hope – this is easy to clean.

Using distilled, mineral-free water will also prevent scale build up in your humidifier.

How To Descale A Humidifier

To descale a humidifier, follow these simple descaling steps:

  1. First, unplug your humidifier and empty the tank.
  2. Use a food grade 3% hydrogen peroxide solution (available at Amazon) to wipe down lose scale.
  3. In case the buildup is too hard, fill the entire tank with the hydrogen peroxide solution. You can also use cleaning grade vinegar (Amazon affl. link) – microwave 1.5 cups of the vinegar for 2 minutes before pouring into the humidifier. This cleaning solution dissolves the minerals and cleans the buildup. 
  4. Leave the solution in the tank for 30 minutes to a few hours, depending on how thick the buildup is. Make sure that the device is unplugged. Do not run your humidifier with the solution inside.
  5. To reach crevices and clean stubborn spots, you may use a soft brush (Link to Amazon) dipped in the cleaning liquid to scrape away the buildup. Do not use sharp objects like knives or blades.
  6. After this, you may also use a dilute bleach solution to further disinfect your tank. Leave this in the tank for 20 minutes.
  7. After emptying the cleaning agent, rinse the tank three or four times with clean water. This is to ensure that no chemicals remain in the humidifier. Otherwise, your humidifier may disperse harmful fumes in the air. Washing the tank repeatedly with water makes sure this doesn’t happen.
  8. Wipe the tank dry with a clean towel. Use only distilled water to avoid scale buildup.

Keep in mind that cleaning instructions may differ from product to product. Follow your manufacturer’s instructions on what solutions you can use to clean your humidifier.

We also recommend cleaning your tank superficially with a solution of 3% hydrogen peroxide every third day even if there is no obvious scale.

Caring For Your Humidifier

Depending on where you live, you may need to use the humidifier all-year-round, or perhaps only for a few months. Humidifiers are commonly used during the dry winter months.

Whenever you use the humidifier, refill the water every day. Empty the tank and use a paper towel to wipe the entire surface. Descale the humidifier if necessary, and refill with pure distilled water.

Even if there is no scale buildup, we recommend wiping the tank with a hydrogen peroxide solution to sterilize it. This keeps your humidifier safe from mold and bacteria.

Most importantly, do not leave stagnant water inside your humidifier. This is a surefire way to encourage bacterial growth, mildew, and mold. When you use a humidifier with stagnant water, this disperses harmful microorganisms into your home.

If you don’t use the device frequently, discard the water, dry the tank, and store your humidifier in a clean, dry area.

Don’t let the area around the humidifier become damp or wet. Don’t place the device over absorbent material like carpets or tablecloths. Do not leave your humidifier too close to drapes or curtains.

The more exposed to air the tank is, the more often you should clean it. This means that if you don’t use your humidifier every day, you ought to clean it before every use as the tank is empty and prone to bacteria while in storage.

If you plan on using a humidifier after it has been put away for a while, rinse the tank with water and 3% hydrogen peroxide three or four times before use.

Monitoring Humidity Levels

The EPA recommends a humidity level between 30 and 50 percent. Low humidity may cause:

  • Dry skin
  • Itchy eyes
  • Sore throat

Invest in a hygrometer to monitor the humidity level of your home. A good humidity sensor will continually monitor the moisture levels in your room and you can adjust how much you use your humidifier accordingly.

As too much moisture can cause bacterial growth, allergies, and respiratory illnesses it’s important to get the balance right. The Govee hydrometer is highly rated on Amazon and you can even set it to alert your phone when the humidity goes out of range. For more information, check it out for yourself on Amazon by clicking on the image below.

The Bottom Line 

A humidifier can make a world of difference to your living space, provided that you use the right kind of water. Investing a few minutes of your day in caring for your humidifier makes a world of difference in the quality of air you breathe. There’s no need to be salty when you go the distilled water way!  

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