Refrigerator Defrost Drain Plugged | How To Fix

Photo of a service man working on a fridge with a pup pulling on his pants

If you suspect that your refrigerator defrost drain is plugged you are not alone. This is actually a very common problem with refrigerators. It starts out as a minor problem but if not corrected can become a major issue.

Each time a refrigerator goes into defrost the frost that has accumulated during the cooling cycle melts and normally runs down the drain. If the refrigerator defrost drain is clogged the water backs up into the freezer and freezes when the refrigerator goes back into the cooling cycle.

So where does all this water come from? Well the water is actually humidity that's in the air. Every time you open the refrigerator door to get a beer, and that is quite often for some of us, humidity from the room rushes in. If the refrigeration cooling system did not remove this humidity then everything in your refrigerator including the walls and the shelving would be saturated with moisture. It's kind of like getting a glass of iced tea on a hot summer day and sitting it on the picnic table. The next thing you know the glass is dripping with moisture. That moisture is humidity in the air that condensed from a gas to a liquid because of the temperature of the glass with all the ice in it.

So a refrigeration system in a refrigerator is designed to remove this moisture and capture it onto the evaporator in the freezer. It does this by forcing the warm humid air through the extremely cold evaporator. When that happens the humidity in the air doesn't go from a gas to a liquid it goes from a gas to a solid and accumulates as frost or snow on the evaporator. The big problem is that if it is not removed eventually it will block the evaporator airflow and you will lose refrigeration. You will first noticed it in the fresh food section when your beer seems warm!

The refrigerator defrost system which includes the heater is located on or near the evaporator. It is designed to melt the frost off so that it drips on to a trough under the evaporator. Then it normally flows into a tube that runs to the base of the refrigerator where it gets heated up and becomes humidity again. If that tube becomes restricted the water backs up and freezes. And this is what you see in a side-by-side refrigerator when you open the freezer door and see an ice skating rink below the bottom shelf on the floor of the freezer. If left unchecked this ice will continue to build up and eventually it will cause a refrigerator not the cool properly resulting in warm beer.

The easiest way for non-technical people to correct this problem is to empty the refrigerator and allow mother nature to melt all of the ice in the freezer around the evaporator drain line. Once the freezer is warm you can remove the cover from the evaporator and flush out the drain with warm water. It will be in the center of the pan located just below the evaporator. Be very careful not to use any tools around the evaporator because it is very delicate. If you poke a hole in the evaporator the refrigerator will be ruined. Some technicians use compressed air to blow out the drain line after it has completely thawed out. Whatever method used warm water or compressed air, flush the drain line a few times to make sure it is completely clear.