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Air Conditioning Checking

Cleaning Your AC Drain Line Regularly Can Prevent System Shutdown

Updated: Feb 10, 2023

One of the many functions of the HVAC system is to remove moisture from the air in a house to provide a comfortable living environment. As this occurs, the moisture must go somewhere; it does not just disappear.

As the HVAC system removes moisture from the air, it collects as condensation on the evaporator coil that then drips into the condensation pan. The liquid then travels through the condensate drain pipe to outside the home where it is dispelled on the lawn or soil area.

Cleaning AC Drain Line

What Causes the Condensate Drain Line to Clog?

In most cases, it is because not only liquid is passing through the condensate drain line. The condensation created by the system can be filled with dust particles as well as bacteria. The bacteria in condensation, with the help of the dust particles, can produce a thick grime or sludge that can be riddled with mold. As this gunk accumulates, the passage of fluid becomes constrained and eventually will stop once the pass is completely blocked.

How often this happens depends on how well you keep your system maintained, how often you replace your AC’s air filter, and the efficiency of your air filter. The MERV rating (minimum efficiency reporting value) of the filter should be at least an eight (8) or higher. A higher MERV rating means that the filter will allow fewer dust particles to pass through.

Even with an efficient air filter, the condensate drain line can still become clogged because the filter will not catch every particle, so you should regularly perform or schedule routine preventive maintenance.

How to Clean Your AC Drain Line With Vinegar or Bleach

To help prevent the build-up and blockage of the condensate drain line there are a few methods of cleaning the drain line. Polyvinyl chloride, commonly abbreviated as PVC, is used for standard residential drain lines. PVC is claimed to be chemical resilient and in many cases can last for several decades.

For many years the recommendation for cleaning the drain line has been to use bleach or white vinegar with hot water as a cleaning solution. These two chemicals work well in clearing the pipe. The ratio is 50/50. Repeating this several times should remove a small blockage.

Please be aware that because of a change in materials used in air handler units, some manufacturers no longer recommend vinegar or bleach due to strong vapors that could cause premature oxidation and degradation of the materials. Studies support similar effects of chemical vapors on copper and aluminum.

As a precaution, Energy Air recommends using only boiling water. With regular AC maintenance, you should not need chemical additives.

The amount of cleaning solution to use varies, but you can determine the amount needed based on the length of the condensate drain line. In single-family homes with an air handler unit in the garage, you will need a minimum of two cups of the cleansing solution. With each additional story that the drain line extends, more cleansing solution may be necessary. It is recommended to start with at least two cups and if the blockage has not cleared, try using more cleansing solution to increase the pressure acting on the blockage.

If the blockage does not clear, a wet-vac or air compressor can be used to assist the clearing of the clog. Proceed with caution when attempting these methods as damage to the system can occur. If the PVC pipe is damaged and not corrected, this could lead to thousands of dollars in repair to drywall and possibly floor.

For more information, check out our step-by-step instructions for unclogging your condensate drain line.

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