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If your trusty humidifier looks murky, you may be concerned about your air quality. So, why does my humidifier water turn black? The answer to that could be anything from dangerous mold to poor water choice.

This article will explain what this black stuff could be and what you can do to get rid of it and prevent it from happening again. It’s important to remedy these issues as quickly as possible since they may impact the air you breathe.

Why Does My Humidifier Water Turn Black?

The black stuff is likely one of two things: mold or minerals. There are three causes of black water in a humidifier. We’ll discuss them below, followed by the best ways to fix the water and prevent this from happening again.

Causes of Black Water in Humidifiers

Black Mold

Black mold is one of the most dangerous colors and got its name because it is a deep black color when it grows. Black mold thrives in damp and dark places, so a humidifier is an ideal place for it to breed.

Because humidifiers are usually wet, many different molds can grow in them, but black mold is by far the most dangerous.

Mineral Deposits

Most of these minerals are in such small amounts they aren’t harmful to humans, but they can be harmful to your humidifier.

As the humidifier sprays out the water, minerals and other impurities remain in the humidifier, sometimes causing the water to turn black or brown. This is normal, and usually, the water needs to be changed.

Impure Water 

why does my humidifier water turn black
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Water contains many impurities like aluminum, iron, ammonia, copper, mercury, silver, iron, cadmium, arsenic, chlorine, and fluoride, to name a few.

This may come as a surprise that you’re consuming all this when you drink tap water, and you probably don’t want it in your air or your humidifier. Using pure water means there are no minerals to get stuck in the humidifier, so only water sprays out.

Destroyed Filter

If you have a humidifier with an air filter, it may be destroyed or worn out. When this happens, it can’t filter out the tiny particles and minerals, and they wind up back in the water basin in large amounts, turning the water black.

How to Fix the Water

If the water in your humidifier is black, the best way to fix this is to clean the humidifier as thoroughly as you can. If the water is black, we recommend cleaning it with a few teaspoons of bleach to ensure you kill all bacteria and remove all residue.

Use a gentle sponge or microfiber cloth to scrape off any black film on the side of your water tank. You should take the time to wipe down the outside of the humidifier with water and bleach to prevent bacteria on the outside from creeping into the water basin.

Make sure you let all parts fully air dry before reassembling. Drying the humidifier with a paper towel or cloth may leave bacteria on the appliance surface.

Neglecting to clean the entire humidifier will likely result in mold or unpleasant odors, or more black water. So take your time and give it some elbow grease.

How to Prevent Humidifier Water from Turning Black

Clean and Disinfect Regularly

Changing the water in your humidifier does not count as cleaning it. To keep your humidifier pristine and black water-free, it needs a thorough cleaning every one to two weeks, preferably once a week.

Cleaning the humidifier also means disinfecting it to kill bacteria and prevent mold. To do this, you can use bleach, citric acid, hydrogen peroxide, or distilled white vinegar. Fill the water tank in the cleaning solution and let it soak while you wipe the rest of the humidifier.

Care for Filter

Make sure you also rinse the air filter, as it may be clogged with tiny particles and debris. Wear gloves and rinse it under a gentle stream of lukewarm water. Be careful not to tear it or let your fingers touch it, as the natural oils will deteriorate it.

If it feels thin or looks worn, consider replacing it. Your air filter in your humidifier should be replaced no less than once a year if you want air to be clean and healthy.

Replace Water Frequently

The best way to prevent mineral deposits and mold is to change the water as frequently as you can. No, you don’t have to change the water twenty times a day, but if you manage 1-3 times every day, this will prevent mold and mineral deposits from forming.

Use the Best Water

By “best” water, we mean to use water with as few impurities as possible. Distilled water that has been boiled will likely have the fewest minerals and toxins, so should not result in any build-up in the humidifier.

You can also use filtered water, which typically is not as pure as distilled, but should still prevent the water from turning black from water impurities. Some people collect and use rainwater because they think it is the purest, but rainwater contains many impurities, so do not do this.

Bottom Line

Black water isn’t good, but there’s no reason to panic. Follow this guide to remedy the black water and ensure it never returns. A murky water tank in your humidifier is rightfully offputting, but hopefully, this article has given you some relief. The key to avoiding these kinds of situations with humidifiers, and dehumidifiers as well, is to clean them regularly and not neglect proper maintenance.


What if my humidifier water turns black all the time?

If you followed all the steps in this guide to remedy your black water, but it is still happening often, you may need to consult an expert.

If the fresh water is turning black almost daily, despite using the right water and performing regular maintenance, there may be something wrong with the unit.

Is the black water harmful to my health?

If the cause of the black water is mold, this is very harmful to your health. If the cause of the black water is mineral deposits, there is zero risk to your health.

And if the cause is impure water, this is also not harmful, or it is as harmful as drinking that same water that isn’t filtered or distilled.