If you do not see ice build-up on the larger copper
A clogged drain line is usually caused by algae build-up inside the drain line. And yes, there is something you can do to prevent this condition. Algae are living plants and will grow in your drain line until they clog the drain line. The air handler provides a cool, damp environment for development of molds and mildew and if left untreated these growths can spread into your duct work. If only moderate to light buildup is present, then there are chemical disinfectants specifically designed for use in air handlers that will kill the existing mold and mildew and control new growth....... These disinfectants are safe and very effective and are applied by simply spraying into the filter intake and by placing 'Algae Strips' directly in the drain pan. If the coil has mold or mildew present then it also should be treated. Make sure that the face of the cooling or evaporator coil is clean so that air can pass through freely. Procedure for cleaning the drain line: The drain should be made of plastic tubing or pipe. If it's black plastic, then you can pull it apart at a connection point. If it's PVC (white) then you may have to cut it and after cleaning, re-connect it with a PVC coupling. You can get a coupling at any hardware store. Whatever you do, DO NOT TRY TO DISCONNECT OR CUT ANY COPPER LINES! The copper lines hold the refrigerant (Freon or Puron) which is under very high pressure. Contractors usually use high pressure gas to blow out the drain line. But, you can clean the drain yourself by disconnecting the drain line at the unit and forcing water, from your garden hose, through the drain line. I had one person tell me he blew it out with his mouth.....Yuck, but It worked! When disconnecting the drain line, keep a bucket nearby as trapped water may come out of it. Don't worry; it will drip out with very little pressure. Another method is to use a shop-vac (wet/dry vacuum cleaner). You can connect it to the drain line where it terminates outside the house, next to the outside unit. Attach the vacuum's hose to the drain line using tape and vacuum for 10 or 15 minutes. After cleaning the drain line, drop an Algae Strip in the drain pan to prevent any further growth. You can also mix some bleach with water and pour it down the drain. And, don't forget! Dirt is the biggest enemy of your air conditioner! Giving your air conditioning system an efficient, high MERV rating air filter is the best thing you can do for your air conditioner. A good air filter will extend the life of your air conditioner because the important parts, like the blower assembly, the cooling coil, and other inner parts will stay cleaner, operate more efficiently and last longer. And, as a side benefit of having a good air filter, your family and you will enjoy breathing much healthier indoor air. Air that will be free of dust mites, mold, mildew, dust, pet dander, etc. etc.