Once a month during the cooling season. That is roughly April through October in Pinellas County — the months when the system runs daily and produces the most condensation.
Why monthly
Algae grows inside the drain line because the pipe is constantly wet and sits in a warm environment. In Florida's humidity, the growth rate is faster than in drier climates. Monthly flushing kills algae before it accumulates enough to block the pipe.
A clogged drain line is the single most common AC service call in Florida. It is also the most preventable. A cup of vinegar once a month prevents a call that typically costs $75 to $150 for a technician to clear.
How to do it
- Find the cleanout tee on the drain line near the air handler. It is a capped T-fitting on the PVC pipe.
- Remove the cap.
- Pour one cup of distilled white vinegar into the opening.
- Replace the cap.
- Done. The vinegar flows through the line and kills algae on contact.
You do not need to turn off the system. You do not need to flush with water afterward, though you can. The next condensation cycle washes the vinegar through.
If your system does not have a cleanout tee
Some systems, especially older installations, do not have a cleanout fitting. Without one, you cannot pour anything into the line without disconnecting the pipe. Ask your technician to install a cleanout tee at your next maintenance visit. It is a small PVC fitting — quick to install and it gives you access for years.
During the off season
In the winter months, the system runs intermittently and produces much less condensation. The drain line dries out between cycles, which naturally inhibits algae growth. Monthly flushing is not necessary from November through March. One flush at the start of the cooling season (late March or early April) is enough to start clean.