The main job of an air conditioner is to remove moisture from the room to give us a feeling of comfort. During this process they create a lot of water. How much depends on the humidity in the air, the size of the air conditioner, its operating efficiency, and whether it was installed correctly.

The water extracted from the air during operation falls down the cooling coil and falls into the base. From here follow channels or passages to the rear of the air conditioner. Some of the water is lifted by the fan blades and used to cool the heating coil, while most of it passes to the rear. Once at the rear, it falls off the base and falls to the ground. That is, if everything works perfectly.

The reality of window air conditioners is that they can leak water. One that is leaking can drive you crazy trying to find the cause of the problem. The following are some suggestions for the most common reasons for water leaks.

1. Incorrectly installed.

A window air conditioner should be slightly lower in the rear than in the front. This allows the water that is drawn from the room to drain to the rear of the machine. A difference of one inch is sufficient. This is always the first thing to check. Many are improperly installed in the rush to relieve the heat. If it is installed too low at the front, the water will flow into the room instead of out. If installed too low at the rear, water can roll off the front edges before it has a chance to run into the rear drain.

2. Put ice.

Water that is dehumidified can turn to ice if there are problems with the cooling system. There are many reasons for an air conditioner to produce ice. Remove the front grill while the machine is running. If there is ice on the cooling coil, it probably needs service. For more information, check out our other article: Why Window Air Conditioners Freeze.

3. Air leaks around the air conditioner.

If hot air can get around the air conditioner, you will find cooler and drier air. When they meet, condensation will occur. If water comes out of the front of the air conditioner, inspect to see if it is dripping from the body of the machine or if there are water droplets adhering to the front area. To test, run the machine for 30 minutes and then use a flashlight to check under the front edge of the base. Small water droplets here indicate an air leak problem. Add foam insulation to prevent hot air from leaking out.

4. Blocked drain hole.

The rear of the air conditioner base has a drain hole or slot to allow water to escape. If it crashes, the water can back up. To test, run the machine for 30 minutes and then inspect if it is draining properly. If it appears blocked, use a small piece of wood to open the drain hole at the back of the metal base. CAUTION: Never be tempted to drill holes in the air conditioner body to relieve water build-up. It can result in severe damage.

5. Blocked internal drains.

There are small hallways that allow water to drain from the front of the air conditioner to the rear. If they are blocked, water will collect on the front of the machine and spill onto the floor. If this happens, the air conditioner will need to be removed from the window and repaired.

6. Outside temperature too cold.
This occurs at the end of the cooling season. If the outside temperature drops below 60 degrees Fahrenheit at night, the cooling coil may freeze. If there are no leaks at bedtime but there is water in front of the machine in the morning, suspect this problem. If this problem is suspected, turn the machine off before bed and restart when the day warms up. Alternatively, operate the machine at night with the selector switch in the ‘fan only’ position. This will circulate the air in the room at night but will not allow it to cool down.