Window Air Conditioner Leaking Water (Main Causes & Troubleshooting Tips)

Window Air Conditioner Leaking Water (Main Causes & Troubleshooting Tips)

It’s frustrating to see your window air conditioner leaking water. If you noticed something like this, the first course of action is to call a professional to handle the problem. However, there are instances where the water leaking from your air conditioner is a normal thing.

If the water leaking to your home is a bit excessive, this might be a major concern and you need an HVAC repair company to inspect your air conditioning unit.

We listed down some of the common causes of leaking in your AC unit as well as some basic troubleshooting guides to help you fix the problem.

Common Causes of Leaking Water from your Window AC

1. Condensation Drain Blockage

Among the different causes in this list, condensation drain blockage is the most common reason for water dripping from your window air conditioners.

Your window AC usually works like a dehumidifier as it removes moisture from the air inside the room. The moisture is then collected in the condensation pan, which can be found at the bottom of your AC. The drain pan is connected to the drainpipe through the condensation drain, which is where the moisture should go to.

The problem occurs when the condensation drain is blocked. Mold, dirt, leaves, and dead animals can clog the drain. Because of this, the water will escape from the overflow pan and spill over instead of going through the drainpipe. You will notice that the water is leaking on the inside or outside depending on where your window AC is leaning.

2. Air Filters are Dirty

If you don’t maintain your window AC unit, you can expect the air filters to become dirty in just a few months. As a rule of thumb, air filters should be cleaned at least two times a year.

Dirty air filters can lead to a frozen evaporator coil. As you all know, filters are there to prevent large particles like dust, bugs, hair, and others to enter the window AC. These large particles will get stuck in the air filter if you don’t clean it regularly, which would lead to restricted airflow.

Once the airflow becomes restricted, there will be less air entering the AC. The refrigerant coil is always cold when the AC is on and its main job is to decrease the temperature of the air. If the coil is not getting enough hot air, it will become extremely cold and will start to freeze.

Once the evaporator coil becomes frozen, this is where the leaking water will come from. Once the ice melts, more than 1 pint of water can leak out of the window AC.

Air Filters are Dirty

3. Condensate Pump is Broken

A broken condensate pump is not a common cause of leaking water from your window AC. This problem only occurs when your AC is in the basement or it is below-ground level. Instead of the usual drainpipe, a condensate pump is placed in your air conditioning system to drain the water to the surface.

If there’s a problem with the condensate pump, the excess water will stay inside the window AC and the condensate pan will be filled immediately. The excess water will leak out of the window AC and cause flooding inside your basement room.

4. Condensate Pan is Broken

If you’ve been using your window AC for over 10 years and it only started to leak, the problem is probably related to your condensate pan. This part usually gets damaged over time and it only means that you have to replace or repair it.

All of the moisture that the AC removes from your room goes to the condensate pan, which is located at the bottom of your window AC. Usually, this pan only has a 2-pint capacity, and the water is transferred to the drainpipe through the condensation drain.

Your condensate pan has to be intact and there are no holes or dents on the surface. If your AC is just recently installed and you had a leak problem, it means that the issue happened during the installation of the unit.

If your AC has been operating for over 10 years, the problem is caused by rust and corrosion.

5. Refrigerant Levels are Low

When the refrigerant levels are very low, you can also expect the pressure inside the lines to drop along with it. As such, the heat transfer that your window AC is capable of will be reduced.

Once this happens, the refrigerant lines will be very cold. After a while, it will start freezing since the heat transfer is lower than normal. Once it freezes, it would eventually melt and you will see water leaking inside your house from the window air conditioner.

Refrigerant Levels are Low

6. Installation Problem

What are the chances that your window AC would have water leaking from it as soon as the installation is done? If you didn’t hire a professional to install the air conditioner for you or you tried to do it yourself without knowing anything, you would end up damaging a few parts of your AC.

Improper installation is definitely one of the main causes of leaking water from your window AC. There is a chance the air conditioning is also too big or too small for your home. It’s always better to hire an HVAC technician to make sure that everything is done right.

Window Air Conditioner Troubleshooting Tips

Since we’ve already mentioned the common causes above, you already have a basic idea of the root cause of the leak in your AC. The best tip is to hire an HVAC technician to check your AC unit, but some fixes are very basic that you can literally do it on your own.

We will list down some of the simple troubleshooting tips to help you fix the leak in your window air conditioner.

1. Fixing the Condensation Drain

This is very simple since the drain is mostly clogged when you see water leaking inside your home. Here is a simple guide to help you:

  • Open the backside of your AC unit and look for the condensation drain.
  • Look for something thin that you can use to remove the clog from the drain hole. You can use a needle or a thin screwdriver.
  • Insert the thin object that you found and wiggle it around the condensation drain. This would release the blockage and allow water to flow freely.
  • To know if the leak is already fixed, open your window AC and the excess water will automatically leak out of the drain pipe.

2. Fixing the Condensate Pan

This is a bit tricky because fixing the condensate pan would depend on the amount of damage that it has. If the condensate pan has been punctured during installation, you can just use water-resistant glue to seal the hole.

However, if the problem is due to rust and corrosion, closing the gaps in the bottom of your AC unit would take a lot of time. There is also a possibility that new holes would appear after some time.

The best choice would be to replace the condensate pan or just get a new window AC. You’ve been using it for more than 10 years so it’s not a bad idea to get a new one. Make sure that you look for an AC with a higher EER rating.

Fixing the Condensate Pan

3. Fixing a Frozen Evaporator Coil

Since the problem started with a dirty air filter, the first thing that you need to do is to clean the air filter. Will it solve the problem after cleaning the filter? No! You still need to wait for the evaporator coil to completely unfreeze.

The remaining ice from the evaporator coil will surely leak out of your window AC. It’s better if you can prepare a dry towel so the water will not damage the area surrounding your AC. You have to wait for the unit to stop leaking before you remove the towel.

4. Recharging your Refrigerant Lines

Putting freon in the refrigerant lines is the best solution for low refrigerant levels. Your AC literally needs more freon so you have to recharge it to fix the leaking issue.

You can do this on your own as there are a lot of video tutorials on how to recharge freon. You just need to follow the instructions and you can do it by yourself. However, make sure that you have the tools as it would be very difficult to do this task without the right set of tools.

The best option is to hire an HVAC technician to do the recharging for you. You’ll have to pay for the labor, but it’s better than messing up the recharging task.


Seeing your window air conditioner leaking water is alarming if you have no idea why it’s happening. As long as you know how to troubleshoot the problem, it would be very easy to fix the issue even without hiring an HVAC technician.

You can do it on your own if you want or you can just hire a professional to make sure that the repair would be done flawlessly.

If you have any questions about leaking water in your window AC or the cause of the problem is not mentioned above, you can comment down below and we will help you out.

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