Skip to Content

How to Deal With Common A/C Condensate Drain Problems


The condensate drain system isn't a complicated mechanical component of your air conditioner, but various problems can occur if it's not working properly. These can range from foul sewer odors and a decline in air quality to flooding and significant water damage. Here's how to deal with three of the most common issues that cause drainage system malfunctions.

Noxious Odors From a Dry Drain Trap

In most central air systems, the condensate drain connects to the home's main sewer line to dispose of extracted water. Just like a kitchen sink drain, the line has a trap that holds a small amount of water to prevent sewer gas backups. When you use the A/C for the first time each season, you may notice a sewer odor briefly until the trap fills up. If you're getting a foul smell whenever the blower is running, an HVAC technician may need to adjust the drain line.

Blockages Caused by a Dirty Evaporator Coil

Debris from a dirty evaporator coil can drip down into the drainage system with every drop of extracted water. Over time, the buildup can block the line and cause a condensate backup. If water overflows the collector pan and isn't noticed right away, you can end up paying for costly water damage repairs. To avoid this, make sure the evaporator gets cleaned when a technician performs your spring HVAC maintenance, and replace your air filter monthly when the A/C is in use.

Clogs Related to Algae or Mold Growth

Mold and algae growth can quickly get out of hand in a warm, moist condensate drain system. An overgrowth that clogs the line can lead to a backup and flood, and if mold gets into the ductwork and circulates through your home, your air quality can suffer. If the problem is severe enough, mold can clog the evaporator coil, restrict the system's airflow and cause component damage. Cleaning the pan and flushing the drain line routinely is the best way to control mold and algae.

Visit our website for in-depth information on most HVAC topics, or just give us a call (408) 868-5500.

Share To: