Window AC Leaking Water? – 6 Common Causes & Solutions

It is great to have a window air conditioner running in the dog days of summer, but things will change when it begins to leak water. After all, not many people know how to deal with it.

If you are facing the same issue and don’t know why your window air conditioner is leaking water, don’t be alarmed, I have the answer. 

Usually, common causes of a leaking window air conditioner include a clogged drain pipe, a damaged drip pan, dirty filters, refrigerant leaks, improper installation, or a damaged condensate pump.

However, this is only a brief response. This post will go over all of the reasons and solutions. Hopefully, it will point you in the right direction and get the leak fixed as soon as possible.

1. Clogged drain hole or drain hose

Window air conditioners produce less water than a central air conditioning system. Some window air conditioners don’t drip water by using the collected water to cool the condenser via a slinger ring. 

However, if your models are relatively old, the water still needs to be drained through a drain hose. 

During the dehumidification process, dirt, dust, or even the rusting material of other parts will fall into the drain pan. With time, it will gradually clog the hole and hose. 

Since the collected water can’t drain outside, it will back up and leak from your window AC.

This is the most likely cause if your leaking window air conditioner hasn’t been serviced for a long time.

How to fix it?

Luckily, this is easy to fix. Once you’ve located the drain hole, disconnect it from the hose and use a soft cloth to remove any buildup around it.

To remove slime or gunk from the drainage hose, use a vacuum cleaner or a wire brush. Pouring vinegar or bleach through it can aid in the prevention of future growth.

2. Damaged drip pan

This is another cause of water leaking in window AC that often happens in old units. Since the drip pan is made of iron, it is more prone to rusting and corrosion. After a few years of use, cracks or holes in the pan may appear, and water may leak from these locations.

How to fix it?

AC drip pans are light on the pocket. Therefore, your best bet is to replace it with a new one.

However, if you are not in a position to do so, you can remove all of the remaining water in the pan and then plug the holes with acrylic, epoxy, or polyurethane sealants.

3. Dirty air filters

Even though they are invisible, there are numerous contaminants lingering in the air. The air filter will remove a portion of those particles as the blower draws in the air, which is great for improving air quality.

However, the filter will get clogged if you don’t clean it regularly, and the reduced airflow will cause the evaporator coil to freeze. If the ice begins to thaw and the excess water is not quickly drained, it will leak inside or outside your home.

How to fix it?

Cleaning or replacing the air filter can solve the problem right away. Simply remove it from your machine, rinse it under running water, thoroughly dry it, and then replace it.

4. Refrigerant leak

In normal circumstances, the refrigerant will circulate between coils and compressor and remain intact.

Nevertheless, due to corrosion, extreme weather, or other factors, the coils will crack, and the refrigerant will leak from these cracks and holes. When the refrigerant level falls, it will absorb more heat than usual, causing your window AC to freeze.

Similar to the dirty filter mentioned above, it will eventually lead to water leaking from your window unit when the ice starts to melt.

How to fix it?

The refrigerant leak could be more of a problem than you realize. Because refrigerant is toxic and harmful to the environment, it should only be handled by a qualified HVAC technician.

These professionals will be able to locate the leak, repair it, and then recharge your machine.

5. Improper installation

Poor installation could be to blame if you just got a new unit and it already started to leak. 

Different from installing other types of air conditioners, window ACs need to be a bit tilted backward. This will help to drain water outside. 

Besides, other possible negligence in the installation can also cause the issue.

Problems may occur if you just relocate your appliance. 

How to fix it?

After cutting off the power supply, you can try to adjust the position of your window unit to see if the problem is remedied. 

If it doesn’t work, you should make a call to a professional. 

6. Defective condensate pump

Unless your machine is underground, most window air conditioners do not require a condensate pump to drain water.

This small device is responsible for pumping water to the surface, which can work against gravity.

When it fails, the condensate accumulates in the drain pan and eventually leaks from your unit.

How to fix it?

Unfortunately, it is another task you should leave to a technician. If your unit has a built-in pump, things could get even more complicated. In many cases, they will suggest you replace it with a new pump since a pump is inexpensive.

To sum up

Water leaking isn’t fun and could become an expensive issue if you leave it unattended. If you notice your window ac leaking water inside or outside the house, you should take measures as soon as possible.

Fortunately, in most cases, cleaning the filter or unclogging the drain pipe will solve the problem. However, if your window unit is over a decade old, the drip pan or coil may be damaged, or the condensate pump may be malfunctioning. A professional should repair these.

If you have a new unit and it immediately begins to leak, there should be some installation issues.

Hopefully, this guide has assisted you in resolving the leakage issue with your window AC.

Have a wonderful day!

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested a lot of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.