Why is my air conditioner leaking?

One of the most common service calls here in South Florida we get on a daily basis is for water leaks coming from the air conditioner unit. This also happens to be one of the issues that need to be addressed quickly, because we all know that water can be a very destructive element. Water damage is very common and can be very costly to repair if the issue is not resolved in a timely manner.

So I’m going to start with “Why and Where does the water come from?”

What most people don’t realize is that your air conditioner system doesn’t only cool the air inside your home, it is also removing the humidity from the air. As the hot humid air enters into your air handler unit inside your home, it passes over the units cold evaporator coil to cool the air down. As this is occurring, condensation/water droplets form on the evaporator coil (think about when you have an ice cold glass of water outside on a hot summer day). As the water beads up, it flows down the slanted coils into a condensate drain pan located inside the unit, which then follows the slope into your condensate drain line (usually a white PVC/plastic pipe coming out of the unit). That drain line usually goes into a wall or into the floor where it exits to the exterior of the home and drains out. (Note: some people may have a condensate pump between the drain pan and drain lines, this is necessary if the drain line is unable to follow a downhill slope to drain properly.)

Next question has several different answers, but now that I’ve explained Why and Where, the next question is “Why is the air conditioner leaking water?”

1. The most common cause of air conditioner water leak issues is a clogged condensate drain line.
   The most common culprit of a drain line clog in your air conditioner unit is algae build-up. Algae thrives inside dark moist places and can form and grow rapidly. If the algae is left untreated it can create a blockage inside the pipes and prevent the water from draining properly, which in turn results in a water back-up and sometimes a water leak.
2. Another common cause of air conditioner water leaks is a frozen evaporator coil.
   If and when your evaporator coil freezes and starts to thaw or melt, the amount of water may be too much for the system to flow and drain properly. As to why your coil is frozen, there are several different answers, the most common being a dirty air filter, dirty evaporator coils or low refrigerant charge. (Look for a more detailed blog post on this topic at a later date).
3. Installation issues may also be another common cause of water leak issues.
   If the air conditioner unit was recently installed, an improper leveling of the unit may not be allowing the water to follow the correct slope and drain properly, this can cause water to buildup inside the drain pan and now allow it to reach the drain lines. Improper piping can also lead to this issue as well.

Finally, the answers you’ve been waiting for “How can I fix the water leak from my air conditioner system?”

Air conditioner manufacturers recommend routine maintenance on your air conditioner systems, the recommendation is twice annually (once in the spring and once in the fall). Any contractor performing a maintenance on your air conditioner should be cleaning your condensate drain pan and condensate drain lines.

1. As a homeowner, you should also be performing your own routine maintenance on the system monthly. In addition to changing your air filters, I recommend you pour a half cup to 1 cup of bleach down your condensate drain line (you should have an access port on your drain line, if you do not, ask your contractor to add one for you), this bleach will help break down and kill any algae buildup inside the drain line.
2. Have a safety water sensors installed on your air conditioner system. They come in many different forms (float switches, electronic sensors, alarms, etc). These devices are designed to either shut down your air conditioner system when a back up is detected to prevent water from reaching the point where it can overflow and cause damage or have an audible alarm which will notify you if a water leak is detected and allow you to respond to the situation.