Why Is My Window Air Conditioner Leaking Water and How to Get Rid of It?

Anytime your house is leaking water, it causes concern. When you come home and see water on your floor, you will quickly investigate the source. Is the sink leaking? Did the toilet overflow? Is the window air conditioner leaking water inside my house?

Discovering your window air conditioning unit is leaking inside can feel devastating. You may ask yourself why is my window air conditioner leaking water and how I can fix this? The smallest leak can damage your floors, carpets, tile, furniture, walls, ceilings, and furniture. Water damage can eventually lead to structural damage in your home.

If your window AC leaks water inside or outside your home, you should act immediately. It does not take long for water to cause damage. It will seep into your carpets and cracks on your floors. A dark and damp environment is the perfect condition for mold growth. Mold growth only takes 24 to 48 hours.

The longer you wait to address the leak, the more damage will occur. There are some steps you can take before calling a professional. Please note: Air conditioning units are different than central air units. This article discusses the inner workings of a window air conditioning system.

AC Working Principal

AC Working

Before you can understand why your AC unit is leaking, it is important to understand how an AC unit works. Air conditioners operate by transforming one phase of matter into another. When gas changes to liquid, it releases heat. An air conditioner uses a refrigerant contained in its tubing to encourage the phase conversion process.

Refrigerant is pulled through the compressor in the form of vapor. The compressor increases the density of the vapor and removes heat. The vapor travels through the air stream and runs over the condenser coils. It is then vented to the exterior side of the building.

Air conditioners also act as a dehumidifier. Moisture is removed as the warm vapors travel over the cold evaporator coils. This process is like that of a radiator in your vehicle. If any of these parts break, become clogged, or fail, you will experience water leaking inside and/or outside your home.

Why Is My Window Air Conditioner Leaking Water Outside

 Air Conditioner Leaking Water

The most common reason for a window air conditioner leaking water is because of a small hole on the back of the unit.

There are a wide variety of reasons why your window AC is leaking outside. Is the drain blocked? Is the air filter dirty? Does the AC have grime or mold build-up in the drainpipe? The common problems that cause your AC to leaks are simple to fix without professional help. They also are inexpensive if you require professional help.

It is important you take preventative measures each year before using your window AC. You should have your AC serviced before the summer months. In the springtime, professionals will examine, clean, and prep your AC to ensure it is working efficiently and it does not leak.

Blocked Drain

Air conditioning units are responsible for removing humidity from your home. It is difficult to cool an area with high humidity. Part of the cooling process is removing this humidity. The drain line removes the condensation and humidity. It drains water out of the unit. Over time, the drain pipe can become clogged. The water will back up and spill out of the drain pan. This will result in a leak.

When you come home and find your AC is leaking, you should check the drain line. The drain line is one of the most common reasons your AC is leaking. It is an easy and affordable fix. An HVAC technician will use equipment called a wet/dry vacuum. This vacuum will remove any mold, dust, or dirt build-up and clean your AC’s drain line.

Air Filters Are Dirty

It is crucial to clean air filters regularly and adequately not to damage the AC system.

After discovering a puddle of water on the floor, you may wonder, “why is my AC leaking water” or “why my AC is leaking water outside.” It could be due to a dirty air filter. When the air filter becomes clogged, moisture will build up in the AC unit. A dirty air filter can also cause negative health side effects and be detrimental to those with allergic respiratory disease.

According to the

US National Library of Medicine and the National Institute of Health, “Air filtration is frequently recommended as a component of environmental control practices for patients with allergic respiratory disease” (Sublett, 2011).

The research displayed a direct link between cleaning air filters and improving the treatment of allergic respiratory disease.

Wrong Installation

If your window AC was installed incorrectly, it could cause leaking. The AC must be installed properly as the manufacturer instructs. For example, water may start dripping if the AC is not sealed properly or at a poor angle. The system needs to be sealed properly to function at its highest efficiency. You should try shutting off the system and reinstalling it.

Not-Working Condenser Pump

Expert HVAC professionals will advise you a small amount of water in your window AC’s drip pan is normal. It should not raise concern. How an AC works, as discussed previously, will cause the warm vapor molecules to condense and form water. The water collects into the drainpipe, through the drain hole, and into the drip pan.

The condenser pump will remove the water once the water reaches a specific level. If the condenser pump is broken, it will not trigger water removal. The water will overflow and cause leaking. Attempting to replace a condenser pump is difficult. You should call an HVAC technician if you believe your condenser pump is broken.

Low Refrigerant Levels

When the refrigerant levels drop in your window AC, the cooling coils have to work harder to cool your home. Less heat will be removed from your home, causing the coils to struggle. Your window AC will operate less efficiently and require more electricity.

You will notice your electric bill quickly rising. It is possible to replace the refrigerant in your AC; however, it is much safer to hire an HVAC professional, so you do not cause any further damage to your AC unit.

How to Fix Window AC Leaking Water

How to Fix Window AC Leaking Water

The damage that results from a leaky AC unit can be costly and annoying to fix, but it’s necessary to do when you want to prolong the AC life.

After your window AC is installed, you may wonder how to clean a window air conditioner without removing it. You can check items like the drain filter, the drainpipe, and the air filter without removing your AC from the window. If you cannot solve why your AC is leaking, you should employ a professional.

Check a Drain Hole

Check a Drain Hole

To inspect the drain hole, you will have to remove the access panel. First, you should turn off the power to the air conditioning unit. Once the access panel is removed, you can inspect the overflow pan and use a flashlight to look for clogs in the drain line.

A tell-tale sign there is a clog in the drain line or drain hole is if there is condensate in the overflow pan. You can also run a simple test by pouring water into the overflow pan. The water should flow freely out of the drain line through the drain hole.

Correct Installation

There are many air conditioners on the market that are affordable and easy to install, like the MIDEA MAW06R1BWT. These air conditioners simply slide into the window. You will not need to make huge modifications to your window for correct installation.

Other bulky air conditioners require you to drill holes and reshape your window. To prevent leaking, you should always follow manufacturer installation instructions.

Clean a Filter if Necessary

The air filter inside your window AC must be cleaned regularly, or it may stop working. A dirty air filter can lead to leaking. You will want to unplug your air conditioner and remove the front panel. Behind the front panel, you will see the filter.

You will remove the air filter, vacuum any dust or hair, and wash the filter with warm and soapy water. Before you reinstall the air filter, you should ensure the air filter is completely dry.

The New York Times spoke with professionals who suggest you clean your air filter before installing it into your window. According to the article, professionals also suggest you clean the window AC filter once monthly during the months of use.

For example, if you run your air conditioning unit from May to August, you should clean the air filter in May, June, July, and August.

There are products like Carbon Pad Filter Rolls you can cut to promote a healthier air filtration system in your window AC.

Consult Professionals

If your window AC continues to leak after you have checked the common issues, you should consult with a professional. You may not feel comfortable removing a panel or cleaning the air filter. An HVAC professional will assess and investigate what is causing your AC unit to leak. They are certified professionals with experience.

Many AC professionals will tell you that most homeowners cause more damage attempting to fix an AC using a DIY instructional video. An AC repairer will come to your home equipped with the parts and the knowledge to fix your AC unit.

Final Thoughts

Every summer, thousands of Americans will find their window AC unit leaking inside and outside of their homes. When you are asking yourself, “why is my window air conditioner leaking water” you should first take the basic measures of checking items like the air filter, drainpipe, drain pan, and overflow pans.

You should also ensure that your window AC unit is installed correctly. It must be sealed correctly in your window. The common reason why your AC is leaking is due to simple and inexpensive solutions. If you have checked the common issues and cannot resolve the leak, you should call your local HVAC professional.


1. Effectiveness of Air Filters and Air Cleaners in Allergic Respiratory Diseases: A Review of the Recent Literature

Recent studies of various types of filtration, used alone or as part of more comprehensive environmental control measures, are reviewed.


2. How to Clean an Air Conditioner | Reviews by Wirecutter

An AC caked in dust is less efficient and can pose health risks. Here’s how to clean and maintain your air conditioner or dusty room fan.


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