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Why is Your Humidifier Water Black? 5 Causes (+ Solutions)

Humidifiers provide numerous health benefits, but black water can be hazardous rather than helpful. If your humidifier stores or release dark water, it’s best to take action as soon as possible. The mixture can cause stains, respiratory problems, and more. It also makes your humidifier much less effective.

Your humidifier water is black because of these explanations:

  • Mineral buildup
  • Bacteria or mold
  • Unclean water in the tank
  • Damaged filter
  • Poor-quality essential oils

Throughout this article, we’ll show you why your humidifier’s water is black, what you can do about it, and how to prevent it from happening down the road. Enjoy!

Hardened Mineral Deposits

If you don’t use distilled water in your humidifier, there’s a high chance you’ll encounter mineral deposits. Most water sources have several types of minerals, including iron, manganese, magnesium, and more. According to Good Humidity, these deposits can leach into the humidifier’s mist and spread throughout the room.

Mineral deposits aren’t too harmful, but they can stain everything in sight. Your carpets, rugs, clothes, bedding, and anything near the humidifier could get stained.

How to Fix

Here’s how you can remove mineral deposits from your humidifier’s water tank:

  1. Unplug the unit and remove the water tank.
  2. Drain the tank and let it dry out.
  3. Pour a 50/50 mixture of white vinegar and water into the tank and let it soak for 30 minutes.
  4. Drain the tank again, then rinse it out with more water (don’t use soap; it can leave a residue behind).
  5. Scrub the water or mist outlet with a toothbrush coated in white vinegar to remove excess mineral buildup.

The best way to prevent minerals from building up in the water tank is to use distilled water. Boiling the water beforehand also gets rid of the minerals, but make sure you filter them out and let the water cool to room temperature before using it in the humidifier.

Bacteria and Mold Growth

Mold and bacteria are two of the most common humidifier problems. Moisture and oxygen combine to invite mold, which covers enclosed portions of the humidifier. The mold or bacteria spreads with the mist when you turn the device on. It’s quite dangerous since mold spores can spread and grow wherever they land.

How to Fix

Much like removing minerals from the humidifier, you can use white vinegar to clean bacteria and mold out of it. It’s best to drain, dry, and scrub the tank with the aforementioned 50/50 water/white vinegar solution. However, some people prefer turning on the humidifier with the vinegar in the tank to flush the whole system.

The primary issue with running white vinegar through a humidifier is the strong scent it produces. We suggest keeping the humidifier outside until the water tank is drained if you prefer this method. It’s an excellent tool to clean the water tank, mist outlet, and water lines.

Dirty, Unhealthy Water Buildup

It’s important to check the water source you use in the humidifier. Failure to do so can ruin the unit and cause air quality issues. Dirty water is any source you get that’s contaminated. It can include dirt, mold, mildew, grime, lead, copper, and more. Inspecting the water before pouring it into the humidifier’s water tank can make a big difference.

How to Fix

So, what can you do to prevent dirty water from ruining your humidifier?

  • Use distilled water in the tank to prevent harsh contaminants from spreading.
  • Never use colored water or drops in the humidifier.
  • Keep a high-end filter in the humidifier to prevent dirty water from leaving the mist outlet.
  • Look for signs of leaks or cracks in the system that could leak contaminants into the water tank.

Dirty water usually has discoloration. It’s best to avoid putting anything other than clean, clear water into the humidifier. This method ensures that you don’t spread unhealthy contaminants into the air or ruin the unit.

The Filter Is Damaged or Worn

Home Air Guides claims replacing the filter is sometimes the only thing you need to do to get rid of the black water. When the filter is broken, small particles flow through the humidifier. Additionally, the filter can deteriorate and mix into the watery mist. Old, worn painted filters and charcoal filters can leak into the water supply.

How to Fix

Consider these suggestions:

  • Replace the filter as often as the manufacturer recommends it in the user’s manual (most humidifiers suggest it between every one to three months).
  • Clean the humidifier monthly to wash or scrub excess grime away.
  • Don’t reuse single-use filters because they’re prone to deterioration.
  • Inspect the filter’s pleats every time you wash it (if they’re broken, the filter cartridge needs to be replaced).
  • Only use filters that are recommended by the company (generic brands are cheaper but can break down and clog the humidifier).

Low-Quality Essential Oils

Many people use essential oils in their humidifiers. If your humidifier allows you to use them (don’t add essential oils to a humidifier if it doesn’t permit them), always use high-end oils. Low-grade drops will bunch together and make a grimy, gross substance in the humidifier’s water tank. This substance will enter the water and turn it black, brown, and many other colors.

How to Fix

Use high-quality essential oils, such as Plant Therapy 100% Pure Lavender Essential Oil. Plant Therapy sells numerous oils that you can safely use in your humidifier. A few drops are more than enough to bring fresh aromatherapy throughout the room or house.

If you use essential oils in your humidifier, we suggest avoiding the budget-friendly multi-packs. These kits usually use impure oils that clog and discolor the water. They might smell great, but these oils can cause a lot of problems in the long run.

Keep in mind that diffusers and humidifiers aren’t the same things. A diffuser can almost always use essential oils, but a humidifier only can if the company allows them. Using essential oils in a humidifier that’s not designed for them will undoubtedly cause it to break down.


  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

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