Why Portable AC Fills with Water Quickly & What to Do

portable air conditioner

Portable air conditioners can fill with water quickly due to the condensation of moisture in the air during the cooling process. Here’s a summary of why this happens and what to do when your portable AC’s water tank fills rapidly:

Causes of Rapid Water Accumulation:

  1. High Humidity: In humid environments, portable air conditioners tend to produce more condensate because there is excess moisture in the air that needs to be removed for effective cooling.
  2. Cooling Capacity: Smaller or less powerful portable AC units may not have as efficient condensate management systems, leading to faster filling of the water tank.
  3. Improper Ventilation: Inadequate ventilation or a poorly sealed installation can allow warm, moist air from outside to enter the room, increasing humidity levels and accelerating condensation.

What to Do When the Water Tank Fills Quickly:

  • Empty the Tank Regularly: The most straightforward solution is to check and empty the water tank regularly. Depending on the humidity level, you may need to do this daily or as often as needed to prevent overflowing.
  • Use Continuous Drainage: If your portable AC offers a continuous drainage option, consider using it. This involves connecting a hose to the unit and directing condensate water to a drain or container. Continuous drainage eliminates the need for manual tank emptying.
  • Lower the Humidity: You can help reduce the amount of condensate produced by lowering the indoor humidity level. Using a separate dehumidifier in conjunction with the portable AC can be an effective way to achieve this.
  • Proper Ventilation: Ensure that the portable AC unit is correctly installed and that the window or vent kit is sealed properly to prevent warm, humid air from entering the room. Proper ventilation can help maintain a more balanced indoor climate.
  • Choose a Higher Capacity Unit: If rapid water accumulation is a recurring issue and the portable AC unit is undersized for the room, consider upgrading to a unit with a higher cooling capacity and a larger condensate collection tank.
  • Maintenance: Regularly clean the unit’s filters and cooling coils to ensure optimal efficiency, as this can help manage condensation better.

How Portable Air Conditioners Work

Portable air conditioners work just like all other air conditioners. Although its primary function is cooling the indoor air, it also helps to lower the relative humidity inside the house.

It contains the following components:

  • Evaporator coil
  • Condenser coil
  • Compressor
  • Refrigerant
  • Blower fan

When the temperature of the indoor air exceeds the set value, the unit kicks in. The blower fan pulls the hot and humid air from the room and pushes it across the evaporator coil.

The evaporator coil contains a cold refrigerant which as you know has a low boiling point but high latent heat of vaporization.

The refrigerant absorbs heat from the air and as it evaporates and exits the evaporator coil and enters the compressor it takes away the heat with it. That is how the indoor air is cooled.

Cooled air is then blown out of the unit and back to the room. The relative humidity of the air being released back to the house is usually is however less than the incoming air.

how portable air conditioners work

The reason for that is that as the air is being cooled by the evaporator coil, the moisture in the air condenses upon contact with the cold coils. The condensate drips into a bucket at the bottom of the unit which you need to empty once full.

The relative humidity levels in your area will determine how often you will need to empty the bucket. Also, folks who own dehumidifiers will empty the bucket fewer times than those who don’t have a dehumidifier.

For those who own a portable air conditioner besides having a central AC system. Most of the humidity will be removed by the central AC and hence it will take longer for the portable AC bucket to fill. However, if you only have a portable AC unit, expect it to fill with water quickly especially in humid locations.

Since portable ACs do not have an outside unit to release the heat absorbed to the outdoors, they have an exhaust hose which is vented out through the window. Some modern portable AC units are self-evaporating which means that instead of manually draining the bucket, the water drains out through the exhaust hose.

Why Your Portable Air Conditioner Fills with Water Quickly

Now that you have an idea of how your portable air conditioner works, let us look at the various reasons as to why it could be filling with water too quickly.

The following are the reasons why your portable AC unit is filling with water too quickly:

1. High Humidity

condensation on a window due to high humidity

Humidity is defined as the amount of water vapor in the air. Specifically, we use relative humidity which is the amount of water vapor expressed as a percentage of the total amount of water the air can hold at that temperature.

As you can see, relative humidity is a function of temperature. That is why relative humidity is high during summers and low during winters.

Apart from that, relative humidity is also dependent on location. Coastal areas or areas near water bodies have high relative humidity (because of evaporation from the sea) than areas farther away from water bodies.

That is why you will find that the relative humidity of Florida on average is 74.5% while that of Arizona is 38.5% despite it being hot. The air in Arizona is hot but dry while the air in Florida is hot and humid.

If your portable air conditioner is filling with water way too quickly, you need to first determine your location’s relative humidity. Do you live in a humid city/town?  The top 10 most humid states in the United States are:

  • Alaska (77.1%)
  • Florida (74.5%)
  • Louisiana (74.0%)
  • Mississippi (73.6%)
  • Hawaii (73.3%)
  • Iowa (72.4%)
  • Michigan (72.1%)
  • Indiana (72.0%)
  • Vermont (71.7%)
  • Maine (71.7%)

The above are averages but expect summer humidity levels to be higher. If you live in such humid areas and your portable AC is filling quickly, it probably is just doing its job.

2. First Start of the Season

As you already know, air conditioners don’t run throughout the year. At some time you will have to turn them off and probably fire up the furnace/heat pump.

Just before indoor air temperature starts to increase and you feel the urge to plug in your portable AC, moisture will have accumulated inside your house especially under carpets, rugs, in furniture and other areas of your house that are likely to hold moisture.

The first day you turn your portable AC on, its main responsibility will be to pull out all that moisture and condense it. You will therefore notice that the AC will fill up with water way quicker than usual.

If this is the scenario in your house, you have no reason to be alarmed. Just give your AC a day or two and it will go back to its normal filling schedule/routine.

3. It Is a New Air Conditioner?

New portable air conditioners may behave just like old air conditioners being turned on for the first time during the season. It may therefore not be something to be concerned about.

If you didn’t have an air conditioner before and you have just installed a new portable AC, it means that there is a lot of moisture trapped inside your house (rugs, carpets, furniture etc.) and not just the usual humidity in your indoor air.

As a result, the new AC will need to not only remove the moisture in the air (humidity) but also the extra moisture trapped inside the house. For that reason, you can expect the unit to fill up with water quicker than normal for the first few days.

After a week or so, you will notice that the frequency of emptying the portable air conditioner’s bucket will have reduced. If it doesn’t then the unit is likely faulty, unless the air is really humid.

4. Humidity Air From Outside

Where is your portable air conditioner installed? How likely is it to pull humid air from areas which it is not intended to cool?

To start with, portable air conditioner are either single-hose or dual-hose. Dual-hose portable AC units have 2 exhaust hoses, one for exhausting heat to the outdoors and the other one for ventilation (bringing in fresh air from outside).

If you have a single-hose portable AC, it will create negative air pressure inside the room it is cooling. When the fan pulls air from the room, the air pressure in the room drops forcing air to come in from outside the room.

If the portable AC units is located close to  bathroom which is used frequently (especially if the folks in the house take long hot showers or even soak up in the tub), humidity from the bathroom will be pulled by the unit and forced to condense. In such a case, you can expect your portable AC to fill up with water quickly.

Kitchens are also another source of humidity. Cooking adds a lot of moisture in the indoor air and if that moisture gets to the portable AC it will fill up quickly. If you use your kitchen, a lot, you can also expect your portable AC to fill up with water quickly.

Does your house have a crawlspace without a vapor barrier or whose vents are opened? Raising damp from the ground or humid air from outside could be penetrating your house forcing the portable AC to condense so much moisture that you have to empty it frequently.

Related post: How to reduce humidity in the house.

5. Dirty Air Filter

Apart from cooling your indoor air, air conditioners also have an air filter to clean the air. The fitter removes dust, hair, pollen, dander and other particles from the house.

As is the norm with all air filters, your portable AC filter will clog but unlike in central ACs you don’t need to change it. Cleaning it once in a month (especially in summer) will keep it in good shape.

cleaning AC filter

Anyway, when the air filter is dirty, the airflow to the coil is restricted. That means that only a small amount of air gets to the coil.

Since the evaporator coil is cold enough to handle a large amount of air but now only a small amount is getting to it, the air will cool way more than it should, which also means that more condensation will happen.

As a result, the portable AC bucket will fill up quicker than usual prompting you to empty it. Apart from a filling up with water quickly, you will also notice that the energy efficiency of the unit will be lower since the fan has to worker harder to pull air through the filter.

Reduced airflow as a result if a clogged air filter can also cause the evaporator coil to freeze. When eventually the ice on the coil starts to melt, the bucket will fill up with water rather too fast than it should.

Some portable AC units have a reminder light to alert you when to replace the filter but most don’t.  Cleaning the filter is all you have to do in this case.

Just remove it and clean it using warm water and a brush then put it back. The AC unit should go back to working properly.

6. Clogged Drain Holes

Although portable air conditions as we have seen have air filters, some tiny particles will still manage to pass through. These particles can end up clogging the unit’s drain holes.

Depending on the type/model you have, portable AC units will have drain holes which drain water from the upper section (the coil) into the bucket. The units also have tubes/holes which drain water from the bucket which is usually used to cool the unit.

Dust and other particles can clog these holes and tubes causing your unit to overflow with water. Most of the times when that happens the unit will shut off.

Luckily, unclogging a portable AC units is not that hard. Scrubbing the unit with a brush will remove the gunk and clear the clogs. If that doesn’t work, connect a shop vac to the drain and suck out the gunk.

7. Clogged Drain Line

Portable AC and drain hose

Instead of manually draining water out of the unit, most portable AC units give you the option to connect a drain line.

Does your portable air conditioner have a condensate drain through which it automatically drains the water to the outside? There is a chance that it could be clogged, restricting the water from draining out of the unit.

To unclog the condensate drain line, start by disconnecting it then use a flexible wire or snake to clean it. If that fails, connect it to a shop vac and suck out the clog.

8. Faulty Condensate Pump

If your portable AC uses a drain to drain the condensate to the outside then it also uses a condensate pump to pump the water out of the room. If it is filling with water rather quickly then the condensate pump could be the problem.

Instead of bringing a technician to try and fix the problem, I would recommend replacing the pump. The pump is inexpensive and you can easily replace it on your own.

9. Faulty Blower Fan

An air conditioner’s fan is responsible for pulling warm and humid air from the room and forcing it through the evaporator coil for cooling, and then supplying it back to the room.

A properly functioning fan will deliver a certain amount of air at a time to the coil. The amount of air delivered is determined by the fan’s speed (revolutions per minute (RPM)). RPM can be affected by a faulty fan or fan motor.

Anyway, when the fan fails to deliver enough air to the evaporator coil, the coil will become colder than it should and it will freeze. A frozen coil will keep defrosting in between cycles, filling the unit will water quicker than normal.

After the portable AC kicks in again, the coil will freeze again and the cycle goes on and on. You may also notice that the AC unit is not cooling effectively.

Stat by inspecting your portable AC fan blades, if any of the blades is broken, even if the RPMs are sufficient, the airflow to the cooling coil will be insufficient and the bucket will fill up with water quickly.

If the fan’s low speed is caused by a bad motor (you can tell that by measuring continuity and other tests), it will need to be replaced.

Unfortunately, problems involving the fan or motor will need to be fixed by an HVAC technician which needless to say is not cheap.

10. Dirty Evaporator Coil

portable AC

Just like a dirty filter, a dirty evaporator coil will limit the air being cooled, and it make cause the coil to freeze. A frozen coil as we have seen will keep defrosting in between cooling cycles forcing the AC to fill up with water too quickly.

Regularly cleaning your portable air conditioner’s evaporator coil will prevent it from freezing and filling the drain bucket too soon.

Wrap Up

And basically those are the reasons why your Portable air conditioner fills with water rather too quickly than it should. I hope that this guide was helpful to you.