How to Use a Dehumidifier

Co-authored by Victor Belavus

Last Updated: March 15, 2024 Approved

Dehumidifiers are designed to regulate the amount of moisture that is in the air of a given space. These machines can be portable or installed more permanently in your home, and they can be used to reduce the relative humidity level in your home, reduce allergies or other respiratory health problems, and make your home more comfortable overall.

Part 1

Part 1 of 5:

Choosing the Right Dehumidifier for Your Needs

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The best size of dehumidifier to buy depends on how big the room is that you want to dehumidify. Measure the square footage of the main room where you’ll use the dehumidifier. Match that to the size of dehumidifier.^{[1]
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Choose the right capacity for the dehumidifier. In addition to being categorized in terms of room size, dehumidifiers are categorized according to the level of moisture in a given room. This is measured in number of pints of water that will be extracted from the environment in a 24-hour period. The result will be a room with your ideal level of humidity.
- For example, a 500 square foot room that smells musty and feels damp would require a 40–45 US-pint (19,000–21,000 ml) dehumidifier. Consult a buying guide to determine the proper size for your needs.^{[2]
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- Dehumidifiers can accommodate up to 44 pints (20.8197 liters) per 24 hours in a space as large as 2,500 square feet (232.257 square meters).
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Using a larger dehumidifier can potentially remove moisture from a room more quickly. Plus, you won’t need to empty the reservoir as often. However, larger machines do cost more to purchase and they use more electricity, adding to your overall costs.^{[3]
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If you need a dehumidifier for a spa room, pool house, warehouse or other space, you should purchase a dehumidifier that is specially made for these spaces. Consult a home supply store to locate the correct type of dehumidifier for these locations.
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Buy a portable dehumidifier. If you plan to move the dehumidifier from room to room frequently, consider buying a portable model. These often have wheels on the base or are light and easy to move. Having a portable dehumidifier will also enable you to move it around the room.
- If you need dehumidifying in multiple rooms in your house, you might consider ducting a dehumidifier into your HVAC system instead of buying a single room unit.
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Consider which features you need on your machine. Modern dehumidifiers have multiple features and settings, and the more expensive the machine is, the more options it will have. Some of the potential features include:
- Adjustable Humidistat: This feature allows you to control the level of moisture in the room. Set the humidistat to your ideal relative humidity level. Once it reaches this level, the machine will automatically shut off.
- Built-in Hygrometer: This instrument reads the humidity level in the room, which helps you accurately set the dehumidifier to maximize water extraction.
- Automatic Shut Off: Many dehumidifiers will automatically shut off when they reach the set humidity level, or when the water reservoir is full.
- Automatic Defrost: If a dehumidifier is overly used, frost can easily build up on the machine’s coils. This can damage the components of the dehumidifier. An automatic defrost option will keep the machine’s fan running to melt the frost.

Part 2

Part 2 of 5:

Choosing When to Use a Dehumidifier

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1
Use a dehumidifier when a room feels damp. Rooms that feel damp and smell musty have a relatively high humidity level. Using a dehumidifier can restore the room to an ideal relative humidity. If the walls feel damp to the touch or have moldy patches, a dehumidifier should be used frequently.
- Obvious signs that you need to use a dehumidifier are when the windows are covered in condensation, mold is visible, or you see moist or wet stains on the walls or ceiling. However, you may also need to use one if the room smells musty or feels damp or stuffy.^{[4]
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  Victor Belavus
  Air Conditioning Specialist
  
  Expert Interview. 6 May 2020.}
- A dehumidifier is necessary if you have experienced flooding in your home. Use a dehumidifier constantly to help remove excess moisture from the air.
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Use a dehumidifier to improve health problems. Breathing wet air decreases your immune system's ability to fight airborne viruses and seasonal respiratory infections.^{[5]
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Victor Belavus
Air Conditioning Specialist

Expert Interview. 6 May 2020.} A dehumidified room can enable some people to breathe more easily, clear up sinuses, and improve coughs or colds.
- Maintaining indoor humidity within the 40%-60% range helps fight respiratory viral illnesses, including COVID-19, because it reduces the number of infectious pathogens in the air.^{[6]
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  Victor Belavus
  Air Conditioning Specialist
  
  Expert Interview. 6 May 2020.}
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Use a dehumidifier in the summer. Humid climates, especially in the summer, can produce uncomfortable conditions and damp-feeling rooms. Using a dehumidifier in the summer will help maintain a more ideal relative humidity level inside your home.
- A dehumidifier works in tandem with air conditioning units, making your AC work more efficiently and keeping the room more comfortable and cool. This can also potentially result in reduced electricity costs.
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Use only certain dehumidifiers in cooler weather. Many dehumidifiers, such as compressor dehumidifiers, are not very efficient when the air temperature is lower than about 65 °F (18 °C). Cooler weather increases the possibility of frost build-up on the machine’s coils, interrupting its efficiency and potentially damaging its operation.
- Desiccant dehumidifiers are effective for cold spaces. If you do need to dehumidify a cold space, you can purchase a dehumidifier specially made for working at lower temperatures.

Part 3

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Placing Your Dehumidifier in a Room

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1
Allow air to circulate around the dehumidifier. Many dehumidifiers can be positioned against a wall if they have top-mounted air discharge. If your machine does not have this feature, you should make sure that you leave plenty of room around the machine. Do not place it against a wall or furniture. Better air circulation will allow your machine to work more efficiently.
- Aim for about 6–12 inches (15–30 cm) of airflow space around all sides of your dehumidifier.^{[7]
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Place the hose carefully. If you are using a hose to drain the water reservoir, place the hose so that it rests in a sink or tub and will not fall out of the sink. Periodically check to make sure that the hose hasn’t been moved and still drains properly into the sink. Use twine to secure the hose to the faucet if it doesn’t want to stay put.
- Keep the hose away from electrical outlets and cords to prevent electric shock.
- Use the shortest hose possible. Someone might trip over a long hose.
Place the dehumidifier away from sources that create dirt and dust, such as woodworking equipment.
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Set up your dehumidifier in the most humid room. The rooms that usually hold the most moisture are bathrooms, laundry rooms, and basements. These are the most typical places to install a dehumidifier.
- Dehumidifiers can also be used on a boat while the boat is moored to a dock.
The most efficient use of a dehumidifier is to use it in one room with the doors and windows closed. You can install it on a wall between two rooms, but this can detract from its efficiency, causing the machine to work harder.
Many dehumidifiers are wall-mounted, but there are a number of models that are portable. If you can, place your dehumidifier close to the center of the room. This will help the machine work more efficiently.
7
Install your dehumidifier in your HVAC system. Some larger units, such as a Santa Fe Dehumidifier, are specially designed to hook into your HVAC system. These are installed with a duct kit and other installation accessories.
- You may want to hire a professional to install a dehumidifier into your HVAC system.

Part 4

Part 4 of 5:

Operating a Dehumidifier

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Read through the entire owner’s manual for your machine so you are familiar with specific operational instructions. Keep the manual in a location where you can reference it easily.
A hygrometer is an instrument that measures the amount of humidity in the air. An ideal relative humidity (RH) level is approximately 45-50% RH. Going above this level may start mold growth, and below 30% RH can contribute to housing structural damage such as cracked ceilings, separated wood floors and other issues.^{[8]
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Plug the dehumidifier into a grounded outlet. Plug your machine into a three-pronged grounded and polarized outlet. Do not use an extension cord. If you don’t have the proper plug, hire an electrician to install a grounded outlet.
- Always unplug the dehumidifier by pulling the cord at the plug. Never yank on the cord to pull it out.
- Do not allow the cord to become bent or pinched.
Depending on the model of dehumidifier, you may adjust the relative humidity (RH) level, measure hygrometer readings, and so on. Run the dehumidifier until you have reached your ideal RH level.
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Allow the dehumidifier to run through several cycles. The first time you use your dehumidifier will be the most productive. You will be removing the majority of the excess water in the air over the first few hours, days or sometimes even weeks. After the first round, though, you will be simply maintaining an appropriate level of humidity rather than trying to bring it down drastically.
- You will be able to set the amount of humidity that you desire on your dehumidifier when you plug it in.
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Close doors and windows to the room. The larger the space, the harder your dehumidifier will need to work. If you close off a room with the dehumidifier inside, it will only work to remove moisture from that room.
- If you are dehumidifying the bathroom, consider where additional moisture can come from. Keep the toilet lid down so that your dehumidifier isn’t drawing water from the toilet.
7
Empty the water reservoir tray frequently. Dehumidifiers produce a lot of water, depending on the relative humidity of the room in which it is operating. If you are not using a hose to drain the water into a sink, you’ll need to empty the water reservoir tray regularly. The machine should turn off automatically when the tray is full in order to prevent overflow.
- Unplug your machine before dumping out the water.
- Monitor your reservoir tray every few hours if it is particularly humid.
- Check your machine’s manufacturer instructions to determine the approximate frequency for dumping the tray.

Part 5

Part 5 of 5:

Cleaning and Maintaining Your Dehumidifier

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Read through the entire owner’s manual for your machine so you are familiar with specific care instructions. Keep the manual in a location where you can reference it easily.
Before cleaning or maintaining your machine, turn it off and unplug it. This will prevent the possibility of receiving an electric shock.
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Clean the water collection reservoir. Remove the water drip reservoir. Wash it with warm water and a mild dishwashing liquid. Rinse it well and dry it thoroughly with a clean cloth.^{[9]
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- Clean this part of the dehumidifier on a regular basis, aiming for at least every 2 weeks.
- Add an odor-eliminating tablet if there is a smell that remains in the reservoir. These tablets are available at home supply stores, and dissolve in water as the reservoir fills up.
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Check the machine’s coils every season. Dust in the coils can hamper the effectiveness of your dehumidifier, making it work harder and less efficiently. The dust can also potentially freeze in the dehumidifier, causing damage to the machine.^{[10]
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- Dust and clean the coils on the dehumidifier every few months to keep them free from dirt that can circulate through the machine. Use a cloth to wipe the dust away.
- Check the coils for any ice build-up as well. If you find any ice, make sure your dehumidifier is not resting on the floor, as this is where the coolest room temperature will be. Rest it on a shelf or chair instead.^{[11]
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Check the air filter every 6 months. Remove the air filter and inspect it for damage every six months. Check for holes, tears or other perforations that may decrease its effectiveness. Depending on the type of air filter you use, you might be able to clean it and reinstall it in the dehumidifier. Other types need to be replaced. Check your manufacturer’s instructions for specific details about your machine.^{[12]
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- The air filter is typically located in the grill area of your dehumidifier. Remove it by opening the front panel and taking out the filter.
- Some dehumidifier manufacturers recommend much more frequent air filter checks, depending how frequently you use the machine. Check your manufacturer’s instructions for specifics regarding your machine.
Avoid short cycling your machine and ensure the longevity of your machine’s operation by making sure the machine has been off for at least 10 minutes before restarting.^{[13]
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Expert Q&A

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Question

What is a healthy indoor humidity level?

Victor Belavus
Air Conditioning Specialist
Victor Belavus is an Air Conditioning Specialist and the Owner of 212 HVAC, an air condition repair and installation company based in Brooklyn, New York. In addition to HVAC and air conditioning units, Victor also specializes in furnace repair and air duct cleaning. He has over 10 years of experience working with HVAC systems.

Victor Belavus

Air Conditioning Specialist

Expert Answer

Keep your home's humidity level between 40% and 60%. This will help you breathe in healthy air instead of air that's too moist.

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Question

When should I use a dehumidifier?

Victor Belavus
Air Conditioning Specialist
Victor Belavus is an Air Conditioning Specialist and the Owner of 212 HVAC, an air condition repair and installation company based in Brooklyn, New York. In addition to HVAC and air conditioning units, Victor also specializes in furnace repair and air duct cleaning. He has over 10 years of experience working with HVAC systems.

Victor Belavus

Air Conditioning Specialist

Expert Answer

You need to use a dehumidifier when you see moist or wet stains on the walls or ceiling, if the windows are covered with condensation, if the room is musty or stuffy, or if mold is visible.

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Warnings

Discard the collected water from the dehumidifier’s water reservoir. Do not use this water for eating, cooking or washing.

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