Why Does My Air Handler Keep Filling Up With Water?

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When there is water buildup in your air handler drip pan, the first place to look is to a clogged condensate line. However, the simplest answer may not always be the only answer. There are several components to the air conditioning system that may be contributing to the fact that your condensate line is clogged. It also helps to have a basic understanding of the air conditioning system and how it works.

Cooling Your Air

The Freon gas inside your air conditioning system is designed to remove heat from your house and transfer it outside. This movement of heat allows your house to cool. The air handler is inside the house along with the blower fan that circulates the air. Usually the air handler (called an evaporator) and the blower are in a unit together and will have the filter close by. The Freon takes the heat that it collects at the evaporator and is pumped outside to the condensing unit where the fan blows off the heat and cooler gas is pumped back into the house.


Moisture is left on the evaporator when the warm air inside meets with the cool evaporator. When enough moisture is present it drips into a pan. The evaporator works along the same principle of water accumulating (condensation) on the outside of a cold glass. Like a coaster would collect the water from your drink, the drip pan collects the water from the evaporator and it flows out the condensate line that usually leads outside the house.


There are several reasons why the condensate line will clog and then the drip pan will fill with water. One is that the evaporator is filled with debris like hair, dirt or dust. The evaporator will then not operate properly and the humidity level will be higher in your home and in the air handler. Algae will grow in the drip pan and the condensate line causing it to clog. Another reason for a clogged condensate line is that the dirt, dust, and hair can clog it directly. In the wintertime when air conditioning units are not used, the slime or algae can grow then or pests can clog the condensate line from the outside.


Regular preventive maintenance solves a lot of problems. An air filter can be replaced once a month, but in a household with pets or smoking, or during a dry season, it may be necessary to change a filter more often. This keeps the evaporator clean. Occasionally pouring a little bleach down the port of the condensate line will kill any algae. A professional air conditioning company will remove all the dirt from the evaporator and the condenser outside to allow the system to function properly. This will allow a system to work longer and will reduce costs.

Unclogging the Line

If the condensate line is clogged there are several things that can be done to free up the clog. The best way is to try to remove the clog using a wet/dry shop type vacuum. This will usually pull the clog through from the end outside. If your condensate line is removable you may have to take it outside and force water through it with a water hose. It is not recommended that you pour drain cleaners down the line. If you cannot remove the clog call a HVAC professional.


T.J. Allen

T.J. Allen has more than 26 years of work experience. His writings range from works of poetry and prose to political campaigns and websites. His education covers the military, schools, emergency medicine, religious education and psychology and counseling. Allen is an accomplished writer, trainer, researcher, public speaker and beekeeper. He holds a Bachelor of Religious Education from Florida Baptist Theological College.