Black Stuff In My Dehumidifier: What Is It & How To Get Rid Of It?

Dehumidifiers are popular these days due to their excellent performance in regulating indoor humidity levels. Many people have reported that some black stuff appears on their devices after a while, and they have no idea what it is.

This black stuff in the dehumidifier often appears in the water bucket, coils, and air filter. It consists of black mold, dirt, and dust, which can be removed on your own.

I will walk you through the causes and risks of the black stuff and then guide you on how to remove and prevent it in this post. Don’t worry! You can handle it easily.

What is the black stuff in my dehumidifier?

While you can find black stuff in different areas in your dehumidifier, the composition of it is more or less the same.

Black residue is typically comprised of black mold, dirt, and dust. It may contain only one substance at times, or it may contain a combination of these substances.

Note that it doesn’t contain mineral buildups in most cases because minerals will not linger in the air, and the dehumidifier coils nowadays are made of high-quality material, which means minerals will not get into the machine.

Black mold

Black mold refers to an array of molds that have a black color. Among all of these fungi, Stachybotrys chartarum is a type of mold that is often seen in our houses. 

Black mold can disperse mold spores in the air, causing respiratory issues when people inhale it. 

People turn on a dehumidifier when the air is humid. There is a high likelihood that the air is full of mold spores already. When the machine starts to draw the air, a small proportion of mold spores can stick to the air filter. Meanwhile, it can proliferate on the coils.

More importantly, mold spores can sneak into the bucket. If the water in the tank is stagnant, it can become the breeding ground for mold. That’s why you often see black mold inside or on the top or sides of the tank. 

For the same reason, water in a humidifier can turn black.

Dust and dirt

dust and dirt in dehumidifier

Dust and dirt are everywhere. If you live in a dusty place, the air filter is prone to clogging in a short time.

In addition, when the air filter is not so effective in trapping impurities, some of them will get into the machine and then adhere to the coils later. 

You can also find them in the water bucket. They will get into the bucket when you replace water and accumulate together. 

Dust and dirt can also trigger allergic reactions, shortness of breath, and other respiratory issues. As a result, you should remove the black stuff in your dehumidifier anyway.

How to identify black stuff in your dehumidifier?

The way to remove the black stuff varies depending on what the composition is. To identify the black residue in your dehumidifier, you can take a close look at it. 

Mold is typically slimy. If you are still not sure, you can rub it with a tissue. Dust and dirt can settle to the bottom of the bucket or appear as black lint on the filter or coil.

Since it could be a mixture of these impurities in most cases, you may feel it is difficult to identify it. It is not a big idea. By following the cleaning routine in the next section, you can eliminate it, no matter the black residue.

How to remove black stuff in the dehumidifier?

Luckily, both mold and dust are easy to get rid of, and you only need some common cleaning products.

Step 1: Check where the black stuff is

People often see black mold in the bucket when they try to change the water. However, many people neglect the black residue in the filter and coils.

It is possible that black stuff has appeared all over the place because mold spores can travel by themselves.

Therefore, you should check your device to decide which part needs to be taken care of.

Step 2: Gathering the tools

You may need to prepare different tools depending on what and where the black stuff in the dehumidifier is. White vinegar, bleach, detergent, a brush, coil cleanser, a soft cloth, goggles, and gloves may be required.

Step 3: Clean the air filter 

Most dehumidifier air filters can be washed. You can take it out and rinse it under running water. This method will remove all of the dust and dirt. If you find mold on the filter, soak it in a vinegar-water solution for 30 minutes before using it, and then scrub the mold away with a soft brush.

Step 4: Clean the dehumidifier coils

Cleaning the coils is more complicated than cleaning the filter. You should take apart the machine and then rinse the coils with soapy water or a specific coil cleanser. 

Before reinstalling the coil, allow it to air dry.

Check here to know more details about how to clean dehumidifier coils.

Step 5: Clean the dehumidifier bucket

The black mold appears most frequently in the dehumidifier bucket. To get rid of the black stuff inside, fill half the bucket with water and add the same amount of vinegar.

Allow the bucket to sit for 30 minutes after scouring it to dissolve the black residue stuck to the wall.

You can re-wipe the bucket with a brush if any visible mold remains.

The beach is another option for cleaning the bucket. Before taking action, you should put on goggles and gloves.

Check here to know more details about how to clean a dehumidifier bucket.

How to prevent black stuff from showing up again?

I understand that removing these black stuff could be a hassle. If you don’t want to deal with it every so often, there are some actions you need to take. 

1. Empty the bucket every day

Stagnant water is always the culprit of black mold. To keep these contaminants at bay, you need to dump the bucket every day, even if it is not full.

2. Clean the bucket once a week

The mineral buildup and some spores can’t be taken away by water. As a result, you must regularly clean and disinfect the bucket.

3. Clean the air filter once the indicator turns on or is about to be blocked.

Some dehumidifier units can detect the condition of the air filter. The indicator will turn on whenever it is too dirty to notify you.

If your device doesn’t have such a function, you can disassemble the filter when you see a layer of dust stick to it.


If you have used a dehumidifier for a while, chances are you have seen black stuff in it. Fortunately, it is easy to get rid of it. 

As most black stuff is composed of dust, dirt, and black mold, you can use white vinegar, soapy water, or bleach to remove it. While most black residue is in the bucket, you should check the condition of the air filter and coils regularly. 

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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 a lot of products in person, like 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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