In this series, we address the top 3 maintenance tasks a homeowner can do to help increase the efficiency and longevity of their HVAC system.


with White Distilled Vinegar

If changing the filters is the best and easiest way to help with your HVAC system’s performance, flushing the drain line with white distilled vinegar is a close second.


The evaporator coil, located in the AHU (air handler unit), is designed to dehumidify every time the unit kicks on. The humidity removal produces condensation, which is dispensed into the drain line leading outdoors.

A drain line that is not consistently flushed promotes bacterial and mildew growth. Over time, the pipe accumulates sludge, which clogs the drain line, and now your system has a real problem. With no where to go, the condensation produced from the evaporator coil either: (1) overflows, OR (2) “trips” the unit’s safety switch (if it has one), and the unit shuts down to prevent an overflow from occurring.

Periodically flushing the drain line with white distilled vinegar prevents bacterial growth and sludge blockage. As an added bonus, white distilled vinegar is an Eco-friendly solution to this issue, in lieu of harsh chemicals.


How do I flush the drain line?

It should first be noted that not all systems are set up for easy clean-out. If your system falls into this category, Assurance Aire can re-pipe your line to include an access-fitting. This service runs about $100-150, depending on the complexity of the existing pipework. As a rule of thumb, all Assurance Aire AHU installs include a T- or access-fitting for ease of flushing the drain line.

Assurance Aire Installs - Drain Line Access

Assurance Aire installs come standard with easy drain line access.

The following steps should be done when the system is NOT running. If it is, simply wait until the unit kicks off.

  • Step 1. Locate the T- (or similar) access fitting near the AHU.
  • Step 2. Remove top or cap.
  • Step 3. Add 1-2 tablespoons white distilled vinegar, followed by 1 cup of water.
  • Step 4. Replace cap.
Flushing the Drain Line

Flushing the A/C Drain Line with White Distilled Vinegar


How often should I flush the drain line?

We recommend flushing the drain line every time you change the air filter(s). Easy to remember, right? Additionally, we suggest running a full gallon of water through the drain line once per year.


If you would like to have an access-fitting installed, or suspect your drain line is clogged, comment below or give us a call at 321-289-1660.