Why Dehumidifiers Grow Mold

By: Evan Scoboria, Last updated: June 28, 2023

Have you ever wondered why your dehumidifier, a device supposed to help manage moisture, ends up hosting a party for mold spores? In this article, we'll delve into the mechanics of dehumidifiers, explore why they can become mold hotspots, and arm you with practical tips on how to keep your device clean, efficient, and mold-free.

Mold Spore

Why Do Dehumidifiers Grow Mold?

While it may seem paradoxical, dehumidifiers can indeed become a breeding ground for mold, despite their function of reducing excess humidity that typically promotes mold growth. The root cause of this lies in the very operational principles of these devices.

Dehumidifiers draw moist air from the environment and cool it down to condense the moisture, thereby reducing the relative humidity. This condensed water accumulates in the collection tank, often called the bucket or reservoir. If the collected water is not promptly emptied, it can create a damp environment conducive to mold growth. This situation is particularly likely if the dehumidifier is used in a space with poor ventilation or is left unattended for a prolonged period.

Another potential cause is poor maintenance of the dehumidifier. Dust and other airborne particles can accumulate on the dehumidifier's cooling coils and filter. This accumulation impairs the device's performance and provides organic material on which mold can feed and grow.

Therefore, despite the dehumidifier's role in managing humidity and reducing mold risk in your surroundings, neglecting regular emptying and cleaning can inadvertently transform it into a site for mold proliferation. To prevent this, users should regularly clean their dehumidifiers and ensure the collected water is emptied promptly. Using a model with an automatic shut-off feature or direct-drain option can also be beneficial in maintaining a healthy, mold-free environment.

Signs of Mold Growth in Dehumidifiers

It’s one thing to discuss the reasons and potential preventative measures for mold growth in dehumidifiers, but how do you know if your dehumidifier is host to this unwanted guest? Mold, especially in the early stages of development, can be covert, slowly expanding its territory without obvious signs. However, knowing what to look for can help you catch mold growth in its infancy, making it easier to address.

Here are some signals that might indicate the presence of mold in your dehumidifier:

  1. Unusual Smells: A musty or foul odor is the most common and noticeable sign of mold. If your dehumidifier emits a strange smell, especially when running, mold has likely made a home somewhere in the device.

  2. Visible Mold Spots: Over time, mold growth can become visible to the naked eye. You might spot black, green, or white specks or clusters in your dehumidifier's water tank or on its vents. Mold can also appear as a slimy or fuzzy surface.

  3. Allergy Symptoms: If someone in your household suddenly starts experiencing allergy symptoms such as sneezing, coughing, or itchy eyes, it could be a response to mold spores in the air. Remember, a dehumidifier's job is to circulate air; if it's infested with mold, it could spread mold spores around your home.

  4. Decreased Efficiency: If your dehumidifier doesn’t seem to perform as well as it used to, it could be due to mold growth. Mold and other types of buildup can obstruct airflow, reducing the dehumidifier's ability to remove moisture from the air.

  5. Persistent Moisture: If your dehumidifier's tank or other parts seem to have a mold problem. Remember, mold loves moisture, and constant dampness can create a perfect environment for mold growth.

The best way to confirm the presence of mold in your dehumidifier is to do a thorough inspection. If you spot any signs of mold, cleaning the device thoroughly or replacing it if it's heavily infested is crucial. 

Preventing and Removing Mold in Dehumidifiers

It's age-old wisdom that prevention is better than cure, and this adage holds when we're talking about mold growth in dehumidifiers. With just a few regular practices, you can significantly reduce the chances of your dehumidifier becoming a mold habitat.

Tips for Preventing Mold Growth in Dehumidifiers

  1. Regular Emptying: Don't let the water sit in your dehumidifier's tank for long. Make a habit of emptying the tank at least once daily, more often if it fills quickly. This denies molding the stagnant water it thrives in.

  2. Periodic Cleaning: Even with regular emptying, some moisture remains in the dehumidifier and can lead to mold growth. Make it a point to clean your dehumidifier every few weeks, more frequently if your home is particularly humid or if anyone in your household has a mold allergy.

  3. Proper Storage: If you don't use your dehumidifier for a while, don't just tuck it away. Clean it thoroughly, ensure it's completely dry, and store it in a dry place to prevent mold growth during storage.

Of course, despite your best efforts, you might still find mold in your dehumidifier. Don't worry, though—it's not a lost cause.

How to Clean a Dehumidifier to Remove Mold

The cleaning process can be divided into three main parts: the exterior, the interior, and the filter. Remember, safety first: always unplug your dehumidifier before cleaning, and consider using gloves and a mask, especially if you're dealing with visible mold.

  1. Cleaning the Exterior of a Dehumidifier: Wipe down the exterior with a damp cloth. If there's visible mold, use a mild detergent or a solution of one part bleach to four parts water.

  2. Cleaning the Interior of a Dehumidifier: This includes the water tank and other internal parts. Refer to your owner's manual for guidance on disassembling your dehumidifier. Use a soft brush or cloth and mild detergent to clean these parts. Again, for visible mold, use a bleach solution.

  3. Cleaning the Filter of a Dehumidifier: Many dehumidifiers have a removable air filter, which can harbor mold. Remove the filter and clean it according to the manufacturer's instructions. You may need to replace the filter if it is not washable or heavily infested with mold.

When to Replace a Moldy Dehumidifier

Sometimes, a mold infestation can be too severe, or the dehumidifier might be old and inefficient. In such cases, it might be more beneficial to replace the unit rather than attempt to clean it. If your dehumidifier has been a faithful companion for several years, or if mold keeps returning despite your best cleaning efforts, it might be time to say goodbye.

Final Thoughts

Mold in your dehumidifier may seem like a cruel twist of irony, but with some understanding and diligence, it's a problem you can readily solve. By staying on top of maintenance and knowing what to look for, you can ensure your dehumidifier works effectively without playing host to any unwelcome fungal tenants. Remember, it's your home, and you're the one who gets to decide who - or what - gets to stay.