We aren’t plumbers, but because of AC evaporators we fix a lot of plugged drain lines. Surprised? Follow along with me through a little Air Conditioning 101.The AC evaporator coil, part of the AC system usually located in your attic, is where the air in your home gets cooled. Nearly everyone is aware of the compressor and condenser units sitting outside their homes, but most people have never seen an evaporator coil. After the compressor and condenser have dispersed the heat from the refrigerant into the outside air, the refrigerant circulates back into your home as a cool liquid under considerable pressure, ready to continue the cooling process. The AC evaporator coil allows the liquid refrigerant (usually R-22 or R410A) to evaporate inside the copper tubing, which extracts heat from the surrounding air, thus lowering the air temperature. The cooled air is then blown throughout the ductwork by the fan. The metal fins on the AC evaporator act like a radiator in reverse, drawing in heat from the air in your home. The heated, gaseous refrigerant then goes outside to the compressor and condenser to be cooled and turned back into liquid form.
So, what about the plugged drain lines?Besides cooling the air, your air conditioner also removes humidity, which makes the air more comfortable. On hot days an AC evaporator coil can produce as much as a gallon of water per hour, depending on air humidity. A pan inside the coil box collects the water, and a plastic tube carries the water into your home’s plumbing system, usually tying into the drain of a bathroom sink. There are a number of reasons air conditioner drain lines get clogged:
- Soap, shaving lather, hair, grease and other things can block the tube where it enters the bathroom or kitchen drain.
- With age, the collector pan can rust; oxidized metal fragments get washed down the tube, where any sticky substance can cause them to collect and block water flow.
- Mildew and mold can build up in the drain lines, especially late in the cooling season and just afterward, when nights are cooler and the drain line is still wet.