Did your air conditioner (AC) stop working in the middle of the night?  Did you awaken to find that the temperature had risen significantly since you went to bed?  This happened to us about five months after we moved into our brand new home in Florida.  The culprit was a clogged AC drain vent line.  What the heck is a drain vent line and why do they clog up?  This is a very common problem when living in Florida.  The climate in Florida requires the constant running of your air conditioning unit and as a result of the heat, humidity and excessive water evaporation that your AC pulls out of you home creates the perfect storm for a clogged drain vent line.  Most new seasonal homeowners are not aware of this condition or of how to deal with it.

As your AC operates it pulls the warm humid air into the cooling and evaporation chamber of your AC exchange handler where the excess moisture is vented to either a drain in the floor or to the exterior of you home.  Due to the constant on and off conditions of an AC it permits water to sit in the drain vent line from time to time.  Mold and mildew will form in the drain vent line and cause a gooey like substance to form in the line which can and does result in the line becoming clogged.  Once the line becomes clogged the water in the drain line continues to accumulate and eventually it will cause the drain float switch to activate.  The good news is that the activated drain float switch shuts off the AC and prevents the continued accumulation of moisture being removed for the air.  The bad news is that it shuts off the AC. 

The minute that your drain float switch does its job your home is now at risk.  This is especially true for seasonal home owners who live in another state and this occurs.  Left unchecked this creates a situation that in as few as 72 hours could be the start of a mold bloom in your home.  Here is the scenario.  There are three things required to allow a mold bloom to start:

  1. High Temperature
  2. High Moisture
  3. Access to organic material (food)

In Florida it does not take very long for the temperatures to rise especially in the heat of our brutal summers, which, ironically, is the time that most of our seasonal homeowners are away.   As the temperature rises in the home so does the humidity level as the AC has stopped functioning and it has stopped removing the moisture from the air.  The last element organic material is everywhere in your home-think about it; the bedding on your beds, the draperies, the wicker furniture, the carpeting, your imported rugs, the clothes in your closet, your Jimmy Chu leather shoes, the sheetrock on the walls, now are you starting to get the idea?  Organic materials is throughout the house.  Let’s not forget that the AC shutoff due to the failure of the drain vent valve, which, shutoff due to an excess accumulation of water in the drip pan.  This pan water now becomes a breeding ground for mold as it provides an ample water supply.

So, what do you do?  If your AC is not cooling as it should or has stopped cooling altogether or has completely shut off try this simple check before you call the AC emergency service hotline.  Many of our Florida homes have the drain float switch which will be located on the air exchange handler in your home.  It is a white device attached to a pipe that is coming out of the AC and should exit to a floor drain or through the wall/floor to the outside of the home.  The float switch will have a wire(s) protruding from the top that runs back to the AC for it is power source.  The float sits in a “cup” or “well” in the valve inline and will likely be pushed upward from the valve as a result of being in the off position.  This has occurred due to the line becoming clogged and the evaporator pan overfilling with water. If the switch is tripped it has done so in order to avoid major water damage.  You may be able to clear the line on your own if you are prepared for it.  Here are the things that you will need to effect a quick repair:

  1. A small shop vacuum
  2. A measuring cup
  3. Bleach or white vinegar

Now let’s clean the line.  Remove the float switch top that is has been pushed up, gently, and lay it aside, while avoiding damage to the electrical connections.  In most cases, you should be able to drain the line by attaching a shop vacuum to the end of the vent pipe line where it exists in the home.  Attach the vacuum and let it run about 3-5 minutes and you can hear the vacuum that was created and if you cup your hand over the float switch hole you can feel the suction.  Shutoff the vacuum and take a cup of bleach or white vinegar and slowly pour it into the vent drain line and let it stand about five minutes.  This step will help minimize a reoccurrence of mold and mildew build up in the short term.  Be sure to place a catch container at the line exit to avoid the spillage of the bleach or vinegar.  CAUTION:  Avoid exposure of the bleach or vinegar to your eyes and skin area.  See manufacture’s label for exposure treatment care.  

Reattach the shop vacuum and remove the excess bleach or vinegar.  Once you have completed this step remove the shop vacuum and properly dispose of the dirty solution.  As a precaution you should repeat this procedure about once every 90 days especially during peak use season.  This is also a great time to exchange and replace the AC filter.  These simple steps will help you to avoid untimely trouble and cost and may just keep damage from becoming a disaster.