What Type of Water for a Humidifier?

A welcome household staple, humidifiers are a tried-and-true method to relieve many harmful effects caused by a lack of moisture in your home. However, many don’t realize that the minerals and contaminants in the water in your humidifier can be introduced to the air you breathe. The quality of your water affects the quality of your air, and mineral-rich water often causes a deposit of “white dust” that coats everything nearby.

In this article, we’ll walk through why the quality of the water in your humidifier matters, what white dust is, and which types of water are best to use for your humidifier.

Why use a humidifier?

A humidifier produces many benefits for your physical health and the health of your home environment, including:

Providing relief to dry and tight skin
Alleviating scratchy throats and congested sinuses during sickness
Soothing itchy and stinging eyes in low-humidity environments
Creating a healthier habitat for houseplants
Protecting wood from cracking or warping from a lack of moisture, including instruments
Reducing static electricity on clothing, furniture, and other surfaces
Causing indoor air to feel warmer, reducing heating costs

Humidifiers are especially popular in winter, when the air naturally contains less moisture and the benefits of humidifying the air are more noticeable.

Whole-house vs. portable humidifiers

Depending on your budget, the needs of your home, and the humidity of your area, you may be comparing the advantages of whole-house humidifiers and portable humidifiers. Let’s break it down:

Whole-house humidifiers are installed near your HVAC system, ensuring an even distribution of humidity throughout your whole home. Integrating a whole-house humidifier avoids any one room or area in your house fluctuating in moisture, eliminating the need for purchasing and refilling multiple portable humidifiers. A whole-house humidifier typically has a lifespan of 10–15 years.

Portable humidifiers are typically placed on an elevated surface near a power source. Using a portable humidifier is more cost-effective than a whole-house system and can provide a higher concentration of humidity for a specific area or a specific purpose. A portable humidifier generally has a lifespan of 5–10 years, depending on the frequency of maintenance.

How does a humidifier work?

Warm mist humidifiers use heat to create steam, while cool mist humidifiers use ultrasonic, impeller, and evaporative models.

Ultrasonic humidifiers use high-frequency vibrations to break water into a fine mist.
Impeller humidifiers use a spinning disc to break apart water drops into tiny droplets, forming a vapor.
Evaporative humidifiers, the most common type of humidifier, use a wick to draw water from a reservoir and a fan to evaporate the water from the wick, creating mist.

Because of the burn risk to children and pets from portable warm mist humidifiers, cool mist humidifiers are considered the safer option. Regardless, all humidifiers perform the same function: to introduce moisture into the surrounding air using a reservoir or source of water.

Why water quality matters for humidifiers

The quality of the water you pour into your humidifier’s reservoir can significantly affect your humidifier and your air quality.

Impact on humidifier performance

Impurities in water can lead to mineral deposits building up on the humidifier mechanism, including the wick that draws up the water, and reducing the efficiency of the humidifier. Minerals in the water are often left behind on the wick, lowering the amount of mist, posing a risk to air quality, and requiring more frequent cleaning.

Calcium and magnesium affect water quality the most; even a small amount in your water will coat the wick. This buildup can increase the risk of damage and the need to clean and maintain the humidifier, shortening its lifespan and resulting in the time or expense of repairing or purchasing another humidifier.

Impact on air quality

Every time you fill your humidifier with water, you’re choosing your air quality as well. Not only can organic contaminants in your water accelerate the growth of mold and bacteria, but minerals and other contaminants can be introduced into the air from the wick that releases the moisture. When the humidifier blows air on the wick to release the moisture into the air, it also blows the solution of minerals into the air as white dust.

What is white dust, and how can it be prevented?

White dust is a chalky white powder deposited from mineral-rich water that has been evaporated by a humidifier. The minerals in water get left behind on the wick when the water evaporates, turning into a dry dust that eventually blows out of the humidifier. White dust can settle on the humidifier, drift through the air in your home, and coat surfaces throughout your home, requiring constant clean-up.

Because white dust is made of minerals, using mineral-free water in your humidifier is the most effective way to remove white dust. Distilled water and water that has been filtered through a reverse osmosis system are both effective forms of mineral-free water that will not leave white dust deposits when evaporated.

Best types of water for humidifiers

The best type of water to use in a humidifier is mineral-free water, which is distilled water or water that has been filtered using reverse osmosis.

Distillation

Distilled water is water that has already been evaporated and separated from nearly all mineral content. Because of this, evaporating distilled water in a humidifier does not cause white dust. However, distilled water needs to be purchased regularly at a store, or involves a time-consuming process to distill water at home.

Reverse osmosis filtration

Reverse osmosis completely removes the mineral content from your water, along with multiple other contaminants like chlorine, arsenic, and microplastics. Installing a reverse osmosis filter under your sink not only provides you with mineral-free water for your humidifier, but also:

Filters water for other uses, including drinking water and water for your saltwater aquarium
Protects your other household appliances from mineral deposits, including steam irons and coffee makers
Decreases plastic waste by reducing reliance on bottled drinking water and jugs of distilled water

Learn more: Reverse Osmosis vs. Distilled Water

Can you use bottled water in a humidifier?

Bottled water is not generally a reliable source of clean water for humidifiers. The purity of bottled water is not consistent across brands, and, in some cases, may even contain a higher TDS content and microplastics than your municipal water.

Here are the types of bottled water:

Reverse osmosis bottled water often has some minerals returned to maintain a consistent taste.
Spring bottled water contains all the natural minerals from its source.
Distilled bottled water is a good choice of mineral-free water.

Bottled water is preferable to tap water, which will generally contain a higher level of minerals. However, regularly using bottles of water to fill your humidifier produces plastic waste and causes a significant regular expense to maintain.

Can you use tap water in a humidifier?

We do not recommend using unfiltered tap water in a humidifier due to the risk of mineral buildup, white dust, and the spread of contaminants like chlorine or heavy metals. The water quality in your area may vary significantly, meaning the effects on your humidifier and home will also vary.

For example, the severity of the mineral content in your tap water varies depending on your area. West Texas has a high mineral content, unlike Upstate South Carolina, where residents won’t typically notice high amounts of minerals in their water supply. If you’re unsure about the quality of your water, order a water testing kit or speak with a qualified water expert.

How to make tap water safe for a humidifier

Depending on your goal for treating the water for your humidifier, tap water can be made safe for use in a humidifier using these methods.

To reduce microbial contaminants: Boiling water or a UV system can help kill bacteria and other microorganisms. After boiling, allow the water to cool completely before using it in your humidifier. Note that boiling does not remove minerals like calcium and magnesium, which can cause white dust buildup in your device.

To remove both minerals and impurities: A reverse osmosis (RO) system is an effective solution. Installing an under-sink or whole-house RO system can remove dissolved minerals, chemicals, and organic contaminants, providing cleaner water that is much safer for your humidifier.

Is boiling water an effective way to purify it for a humidifier?

While boiling water does kill existing bacteria in your water, it is not an effective method to separate minerals from water for use in a humidifier. Evaporation lowers the amount of water while the minerals remain in the container, meaning the mineral concentration of the water is higher after boiling and nearly impossible to keep separated when using the water.

How to prevent mold in a humidifier

Because mold in a humidifier is caused by bacterial growth from contaminated or stagnant water, it can be prevented by avoiding the use of unfiltered tap water and cleaning the appliance regularly. Unfiltered tap water contains organic contaminants that accelerate the growth of mold. Humidifiers should be cleaned regularly to remove the organic material and prevent growth from contaminants that settle in an inactive or dirty reservoir of water.

How to clean a humidifier

Especially if you are using unfiltered water in your humidifier, be sure to regularly clean it in order to avoid excess buildup of minerals, mold, or bacteria that cause a health risk and lower your appliance’s lifespan. Cleaning a humidifier is a simple process:

Unplug, dismantle, and empty the humidifier.
Wipe down using a mixture of equal parts vinegar and filtered or distilled water. For a deep clean, let the solution sit in the tank for 20-30 minutes before rinsing.
Thoroughly dry all exterior surfaces.
Refill with mineral-free water.
If necessary, replace the wick or filter.

How often you need to clean your humidifier depends on how much you use it and the water you use. Using mineral-free water will protect your home from white dust, but in hard water areas, your humidifier may also need to be checked for scale.

When to replace your humidifier

A portable humidifier needs to be replaced when it shows significant signs of damage or wear, including:

Cracks in the water reservoir
Leaks from external or internal damage
Unusual noise, including rattling or buzzing from electronic components
A damaged cord that causes it to turn off when plugged in
No or significantly less mist or steam from the spout
Odors caused by bacterial growth inside the mechanism

Before replacing your humidifier, verify the filter or wick has been recently cleaned or replaced according to the recommended schedule.

Protect your water quality for all of your household appliances

Your humidifier isn’t the only appliance that can benefit from mineral-free, filtered water. Installing a reverse osmosis system will result in benefits throughout your home by removing minerals and contaminants from your water.

For expert guidance on reverse osmosis filtration, contact the water specialists at Fresh Water Systems—we’re here to help.

You might also like:

Why use a humidifier?

Whole-house vs. portable humidifiers

How does a humidifier work?