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Why Is Hard Water Problematic For Humidifiers

Why Is Hard Water Problematic For Humidifiers?

We can reap many benefits by using a humidifier, such as relieving dry skin, sore throat, and respiratory issues. Since humidifiers work with water, what type of water you use will directly affect the performance of your device. 

Is using hard water in a humidifier a good idea? No. hard water can clog the machine, foster the growth of bacteria and mold, and expel white dust into the air. You should use distilled water if possible.

I will cover more details about why hard water is problematic for humidifiers and how to ease these problems in this post. I am sure you will get numerous helpful tips for adding water to your humidifier.

What is hard water? 

what is hard water

While we often talk about hard water and soft water in our daily lives, most of us don’t know what hard water is exactly. 

Hard water refers to water that contains high levels of calcium and magnesium, and we measure it in GPL (grains per liter) or GPG (grain per gallon). Water that contains 61 to 120 mg/L of calcium carbonate is moderately hard, 121 to 180 mg/L is hard, and more than 180 mg/L is very hard. 

In fact, 85% of American households have hard water. It means that whenever you choose to use tap water in a humidifier, you have to deal with the related problems caused by hard water.

The water is likely hard if you often see the white scale on the faucet or feel a film on your hands after washing it. 

Can you use hard water in a humidifier?

Drinking hard water will not put you at risk in most cases. How about adding it to a humidifier?

While using hard water will not make your humidifier stop working immediately, it is not recommended to do it, especially for long-term use.

Among all types of water, hard water should be the last one you want to use. I will elaborate on the reasons in the following section.

Why shouldn’t you use hard water in a humidifier?

Why using hard water is not a good idea boils down to 3 main reasons.

Clog the machine

mineral buildup of humidifier

Hard water contains more dissolved minerals than other types of water. When the water sits in the water reservoir for a while, the dissolved minerals will settle down and become mineral deposits. 

For those using an ultrasonic humidifier, the mineral buildup can form around the membrane, causing it hard to vibrate as powerful as usual. Then you will see there is reduced mist or no mist coming out of the device. 

Evaporative humidifiers and furnace humidifiers use wicks to filter out impurities. But too many buildups can shorten the lifespan of filters significantly. 

Regarding warm mist humidifiers, the mineral deposits will adhere to heating elements, affecting the machine’s conductivity and efficiency.

Therefore, no matter which type of humidifier you use, hard water can be the culprit of clogging.

Clogs can shorten the lifetime of your humidifiers. You may have to purchase a new one every 1 or 2 years.

Promote the growth of contaminants 

mold in humidifier

Mold and bacteria feed on mineral deposits. As hard water is full of minerals, it can provide more nutrition for these creatures than others. So the water tank will turn to be the breeding ground for them.

These harmful contaminants will not always stay in the water tank as you expect. They will go with the water vapor and get into the air.

Mold spores and bacteria are always looking for a new residence, and when you breathe, they will get into your body, resulting in allergic reactions, asthma attacks, and other infections. Sometimes, people call them humidifier sickness syndromes

People use humidifiers to relieve health conditions, but they may get sick in the end.

Warm mist humidifiers can kill most microorganisms while boiling the water, so this is not a problem. 

Disperse white dust

White dust is a problem that only occurs in ultrasonic humidifiers.

All the ultrasonic humidifiers work on the same principle – breaking down water into tiny moisture particles by means of vibration. Consequently, there is no component to purify the water before releasing it into the air. 

The mineral deposits will also enter the air with water moisture as white dust and lead to respiratory problems when inhaled. White dust will also attach to surfaces, extending your time on cleaning. 

How to deal with it?

If you insist on using hard water for your humidifier, there are a few ways to offset the possible adverse effects. Anyway, distilled water is always the best choice.

Commit to regular maintenance

Cleaning and disinfecting the humidifier can help to kill harmful bacteria, mold spores, and other impurities. It can also reduce the sediment in the tank and base. 

If you use hard water in your humidifier, you need to clean the device more frequently.

Use demineralization cartridges 

Humidifier cartridge

Demineralization cartridges can absorb minerals in the water. By using it, less white dust will get into the air. Meanwhile, the water has a lower likelihood of being the peri dish of microorganisms.

Install a water softener system

The water softener system is not exactly light on the pocket, and it can last for years and send softener water constantly for your whole house. 

Soft water is much better than hard water for humidifier use as it contains much fewer minerals. When having a water softener system installed, water flowing out from the faucet will not be hard water anymore. 

Use a water softener tablet

If you are working on a budget, you can consider using a water softener tablet. Every time you need to refill the water tank, you can use a tablet to reduce the hardness of the water. While it is a tedious task, it is an affordable option you can go to. 

Boil the hard water

This is the easiest way to turn hard water into distilled water. The minerals will be left in the pot by boiling the water, and the water vapor collected is free of impurities. 

Choose a humidifier that works with a filter 

Evaporative humidifiers, drum-style furnace humidifiers, or flow-through furnace humidifiers are better than ultrasonic units if you have to use hard water. The reason is that these models have a filter inside, which can help to filter out impurities. 

The cost of filters will add up with time, but it will pose fewer health risks to you.


We often neglect the hardness of water when adding water to a humidifier. In fact, hard water can wreak havoc on your machine in the long run. 

You can use hard water, but it can significantly shorten the lifespan of your humidifier, clog the machine, and harm your health. This is because hard water contains more minerals, especially calcium and magnesium. 

There are some workarounds, like regular cleaning, using demineralization cartridges, adding softener tablets, or installing a softener system, but distilled water is still the best bet.  

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested more than 150 products in person, including humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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