Why Portable Air Conditioner Fills with Water Quickly?

Portable air conditioners that are self-contained and sit on the floor are one of the popular ways to provide cooling for a room. Standard window air conditioners get rid of excess water through the back of the unit, allowing it to drip onto the ground. Portables are completely inside the room, so they have to handle excess water in a completely different way.

One of the common problems with a portable AC is that of having it fill with water quickly. Now, keep in mind that they are designed to remove moisture from the air. If the unit is filling up quickly, it might be doing its job – or there might be a maintenance issue to consider.

Let’s start here: Knowing how this type of unit is supposed to work is a key to knowing what might be causing the problem, and what can be done about it.

Understanding How a Portable AC Works

Portable air conditioners work on the same basic principle as other true air conditioners. A compressor circulates a refrigerant through a continuous loop that includes an evaporator and a condenser. Warm, humid room air passing over the evaporator is cooled and moisture is removed from it. Heat from the room air is transferred by the refrigerant to the condenser, where it is then vented through an exhaust hose connected to a window kit to the outside environment.

What happens to the excess water that is removed from the room air depends on the particular type and model of portable AC you have.

Some portables allow the water to drain into an internal tub or bucket that needs to be manually emptied from time to time.

Others use part of the water to help cool the unit and a small amount is collected in special cavities inside the unit until a float sends a signal to shut off the AC. Then the water must be drained through a tube, a hose or into a shallow pan.

Still other models are fully self-evaporating, which use part of the water for cooling the unit itself and send the rest of it out through the hot air exhaust tube to the outdoors.

See our Portable Air Conditioner Guide for more details about operation, performance, efficiency and sizing a portable air conditioner.

Why Portable Air Conditioner Fills with Water Quickly?

To begin, it’s good to know that if a portable air conditioner is filling with water, that means that it is doing what it’s supposed to do. It is “conditioning” the air, which involves both cooling and dehumidifying. If by “too often” you mean once a day or every other day, then there probably isn’t anything wrong with the unit. The air is humid, and it’s doing a good job of dehumidifying it. There might be an environmental solution like those discussed below.

However, if you feel that you are having to empty the bucket or drain the unit too often, there are several reasons why this might be happening.

First Startup of the Season

Many people disconnect their portable AC during cold weather and store it in a closet, garage or somewhere else. When the cooling season rolls around and the unit is turned on for the first time, there may be a lot of moisture in the furniture, carpet, walls and ceiling that has built up since the AC was last used. You may experience a lot of water filling up your unit for several days when you first start it up. Once the room air has the excess moisture removed, the AC unit should not fill up as quickly.

Here's another idea. Maybe it wasn’t emptied at the end of the previous season, and it was already half full of water when you turned it on for the first time this season?

If this was the first time you’ve run it this season, the problem of the portable ac filling up quickly with water should diminish as your air dries out.

Very Humid Weather

There might not be much you can do, depending on your climate.

In many climates, humid air is quite normal. For example, both Washington and Alabama have an average Relative Humidity of about 71% - that’s a pretty high average. Other places like Nevada and Arizona are both at about 38% - that’s pretty low. If you live in a humid area – or if it has been a very humid day or week wherever you live – your portable AC is going to fill up with water much more quickly than usual.

Pro Tip: In very humid climates, a fully self-evaporating model is the best choice in portable air conditioners.

Pro Tip 2: If you live in a muggy climate and don’t like emptying a portable air conditioner, we suggest you get one that can run to a floor drain, if a drain is available, or switch to a window air conditioner that can drain continuously to the outside of the window, and you won’t have to bother with it.

Our comprehensive Window Air Conditioner Reviews and Buying Guide is a good place to begin researching a window unit.

Humid Air Infiltrating the Room

Any room air conditioner will be exposed to whatever air is allowed to enter the room in which it is installed. Whenever the AC is on, it will be processing all of that air. Any humid air that comes into the room will result in more water in the AC unit, and that might cause the portable to fill with water quickly.

For example, maybe your AC is in a bedroom that is connected to a bathroom in which showers are regularly taken. Any excess moisture from the showers will be introduced into the bedroom when the bathroom door is opened. This moist air could also come in under the door even when it’s closed.

Another way humid air is introduced into a room is by wet laundry that has been hung here or there to dry. Where is the moisture from those wet clothes going to go? Right into the AC where it will quite possibly cause it to fill with water quickly.

If you have a one-hose portable AC, there is also the fact that because of its operational design, it will pull air from outside the room to make up for the room air that is vented through the exhaust hose. Dual hose models do not operate this way and do not need “makeup” air.

Dirty Air Filter

Every portable air conditioner has at least one filter through which air is drawn in and out of the unit. These will occasionally become clogged with dust, pet hair and other dirt particles. Some models have a reminder light to clean the filter when it’s time. Most do not.

If your filters become too dirty, the AC unit will not be able to circulate air around and through its internal parts properly. The result could be that excess water will accumulate inside your machine much more quickly than normal. Follow the instructions in your user’s manual for proper timing of cleaning and replacing your air filters.

Plugged Drain Holes or Tubes

Depending on the make and model of your portable air conditioner, there might be drain holes to allow the water inside the upper part to drain to the lower part during the cooling process. There may also be internal tubes through which water is pumped to help cool the unit itself. Over time, enough dust or other debris can collect to plug one of these drain holes or tubes. This can result in too much water remaining inside the unit, leading to leaking, with water coming out on the floor. It can also cause the unit to shut down and not restart until the problem is corrected.

This video shows just how dirty a portable AC can get inside – and how to clean it. Eventually, some of this debris will plug the holes and tubes through which water is supposed to drain.

Stuck Float

If your portable air conditioner has the feature that signals when it needs to be drained and shuts off until you do, then it probably has a float. The float will be inside the machine, either in the bottom of one of the water-holding cavities, or in the container that is to be emptied when it’s full of water. When the water level rises to a certain point, the float will tilt enough to send the signal for the AC to shut off. This is to keep excess water from overflowing and leaking onto your floor.

If your portable air conditioner is a few years old, it might have accumulated enough dust, pet hair and other debris inside to cause the float to be unable to lift up to do its job. If you are handy, you might be able to remove the outer cover of your unit, find the float, and clean whatever is interfering with the proper float operation.

Pro Safety Tip: To avoid potential shock, be sure to unplug the unit from its electrical connection before attempting to remove the cover.

Faulty Air Conditioner

Yes, that can happen. It’s an appliance that has both electrical and mechanical parts. We all know that they sometimes fail. Most of the time, one of the 6 reasons above is why a portable air conditioner fills with water quickly. But if you determine that none of these could be your problem, there could be a mechanical reason it shuts off quickly due to being “full,” even if it isn’t actually full.

If you haven’t been able to solve the issue with the help of this Pick HVAC portable air conditioner troubleshooting guide, then it is probably time to get help from a reliable AC service technician or local small appliance repair shop.

Related Article: Why is My Portable AC Not Cooling?

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