How Quickly Should a Dehumidifier Fill Up?

While dehumidifiers reduce moisture in the air, they collect water in an internal reservoir. The time it takes to fill up this container depends on many factors, particularly the dehumidifier capacity, tank capacity, relative humidity, and room size. On average, the standard 20 to 50-pint dehumidifier should fill up its tank within a few hours of continuous operation.

Once the tank fills up, the dehumidifier will shut off automatically. Then, you will have to empty the water by hand and reinstall the tank to resume operation. All the while, the dehumidifier will not remove excess moisture from the air and the humidity level may increase again. Therefore, it’s critical to know when your dehumidifier tank fills up so it can be emptied and resume operation immediately. Below we’ll talk about the factors that affect a dehumidifier’s speed of water collection and answer some common questions that you may have.

Why Do Dehumidifiers Collect Water?

The ideal indoor humidity ranges from 30% to 50%. From 60% and above, the air will be uncomfortable to breathe and even cause a variety of problems in your home. To avoid this, the main purpose of a dehumidifier is to reduce moisture levels in the air. This results in condensate, which is then collected in a reservoir. The dehumidifier’s speed of water collection depends on many factors, particularly the following:

Factors that Affect Speed of Water Collection

Dehumidifier Size

How much water should a dehumidifier collect in a day? It depends mostly on its size. The capacity refers to the maximum amount of moisture the dehumidifier can remove in 24 hours. For residential portable dehumidifiers, this is measured under the conditions set by the Department of Energy. The standard dehumidifier capacities today are 20, 30, and 50 pints (or 22, 35, and 50 pints depending on the brand). 

This is one of the most important features you must look for in a dehumidifier. A higher capacity means the unit can remove moisture at a faster rate and thus will be able to collect more water in a day. However, it doesn’t necessarily mean that a larger dehumidifier will fill up before a smaller unit in different environments.

Tank Capacity

Not to be confused with the dehumidifier capacity, the tank capacity is simply the volume of water the tank can hold. Obviously, a larger tank or bucket can contain more condensate, allowing the dehumidifier to collect more moisture and run for a longer period before filling up. 

A larger dehumidifier usually comes with a larger tank, but the exact capacity varies per brand and model. In any case, a smaller tank will fill up faster. For example, let’s compare a 50-pint dehumidifier with a 12-pint tank to a 50-pint unit with a 16-pint tank. If you run them both continuously for 24 hours, collecting the same 50 pints of moisture, then the 12-pint tank will fill up at least four times and the 16-pint tank three times. This means the unit with a smaller tank will fill up faster, but both units are collecting the same total amount of water within 24 hours. 

Relative Humidity 

Another important factor is the levels of relative humidity in the space where your dehumidifier is running. Higher humidity means there is more water vapor in the air for your dehumidifier to collect. Thus, your dehumidifier can collect more water in a high humidity area. As long as you have the right capacity, the dehumidifier can fill up within a couple of hours in a severely damp space. If there are visible water stains and mold growth in a bathroom, laundry room, and even your living space, you can expect higher humidity level.

Air Temperature

A higher air temperature means the air can hold more water molecules. So when it’s hot outside, you can also expect higher indoor humidity. This is why dehumidifiers lose effectiveness in low temperatures and are most effective in warm and humid environments, collecting water faster on a summer day than on any winter day. In fact, most compressor dehumidifiers may not even work in cold weather. 

Room Size

The room size, usually measured in square feet, also affects how much moisture your dehumidifier needs to remove. Thus, running your dehumidifier in a larger room means it will have to cover more ground and collect more water in a smaller space with similar conditions. Using the same dehumidifier in two rooms with similar humidity levels, with one room significantly larger than the other, the dehumidifier will collect water faster in the larger room.

How Does a Dehumidifier Collect Water?

A dehumidifier removes excess moisture from the air using different methods. The two main types of dehumidifiers are called refrigerant and desiccant. 

The more common refrigerant or compressor dehumidifier works similarly to an air conditioner. It uses a compressor to pump the refrigerant through the cooling coils. Warm, moist air is drawn by a fan and then passes through the metal coils where the vapor condenses into water droplets. This is what your dehumidifier collects in its water tank. The dryer air is then reheated and released into the room.

On the other hand, a desiccant dehumidifier uses a hygroscopic material that binds with the water molecules in the air until the desiccant is fully saturated with moisture. Most desiccant dehumidifiers don’t have a tank that collects water. In the case of moisture absorbers, the desiccant dissolves into a liquid and collects on the bottom of its container. This process can take a few weeks up to months depending on the size of the container. For residential desiccant dehumidifiers with tanks, the saturated silica gel is heated to produce condensate.

How Long Does it Take for a Dehumidifier to Fill Up?

Again, the amount of time it takes for your dehumidifier tank to fill up depends on the factors we discussed above. In general, a high-capacity dehumidifier in a heavily moist space will collect more moisture from the air. On average, standard 20- to 50-pint units might take about six to eight hours to fill the tank with water. Keep in mind that it can take even shorter or even longer depending on the tank size as well as the room size and condition. 

Also remember that when the tank fills up, you will need to empty the water. It’s a relatively easy task but if you don’t want to have to do it multiple times a day, then you should definitely consider other drainage options such as a gravity drain hose and condensate pump. Learn more about your options here.

What to do if your dehumidifier fills up quickly?

There can be many reasons your dehumidifier is filling up its tank faster than usual, but most are not a cause for concern. It can simply be because of sudden changes in temperatures and humidity levels. When you operate a dehumidifier in a humid room for the first time, it may collect a lot of moisture to get the humidity down to your target level. Furthermore, if the unit is coming from a defrost cycle, the melted ice will drip down into the tank and fill it up with water. Check the humidity and temperature in the room to make sure the amount of moisture collected is respective to the changes in the environment. If this isn’t the case, then there might be a more serious problem with the unit’s internal components. It’s best to have your dehumidifier inspected by a professional.

FAQ Section

How long does it take for a dehumidifier to work?

A dehumidifier will start working to remove moisture from the air as soon as it is plugged in and turned on. However, the time it takes for you to notice the effects depends mainly on the dehumidifier capacity, room size, and relative humidity. When using it for the first time, a portable dehumidifier can take 6 to 12 hours to have a significant impact on humidity levels. 

How long should you run a dehumidifier?

Again, the answer varies depending on many factors such as the room size and condition, as well as the unit’s capacity. In general, it’s recommended to run a dehumidifier for 8 to 12 hours a day. It may need to run for a longer time if the place is extremely humid, like a basement with visible damp stains on the walls and floor. 

Why Is My Dehumidifier Running But Not Collecting Water?

If your dehumidifier is turned on but isn’t collecting water after a certain amount of time, it could be that there is simply not enough moisture in the air. Check the humidity in the room with a separate device and make sure you set your desired level t least 5% to 10% below for the unit to start working. Additionally, if the air is too cold, the unit will stop dehumidifying and go on defrost mode. If the unit doesn’t have a Defrost Mode indicator, it may seem like it’s running but not collecting water when in fact, it’s only melting the frost.

How many times a day should you empty a dehumidifier?

Ideally, you must empty your dehumidifier tank as soon as it’s full. This ensures that it’s working as needed and it also reduces the risks of growing mold inside the tank. Generally, you will need to empty the tank at least once or twice a day depending again on room size and conditions. However, even if your dehumidifier doesn’t fill up every day, make it a habit to empty the water and clean the tank after use.

Should you run a dehumidifier constantly? 

No, you don’t need to run your dehumidifier constantly. Turn it on only when humidity levels reach above 50% RH, then turn it off once it reaches optimal humidity levels. Get a humidifier with a built-in humidistat so it will turn off automatically when it reaches your desired humidity.

Wrapping Up

Dehumidifiers naturally collect water in a tank to reduce indoor humidity and keep it within the optimal levels for better air quality. They are rated in pints per day to tell you how much water they can collect in a day, but the actual amount depends on a lot of factors, such as the dehumidifier capacity and the room size and conditions. When the tank fills up, you need to empty the water immediately to resume operation. This can take 6 to 8 hours on average, but again it varies greatly from case to case. To make sure your dehumidifier works efficiently, get the right capacity and tank size for your need.

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