AC Drain Line Clogged? Learn What You Can Do

Before we dive into how to fix the problem, let’s take a moment to make sure you know what your AC drain line is, where it’s located, and how it works.

The AC drain line is located inside your home at the indoor HVAC unit. Your split system air conditioner or heat pump system consists of the outdoor condenser unit and the indoor evaporator coil, housed in the air handler or next to the furnace. As the cooling system operates, it generates condensation at the indoor unit.

These water droplets drain into the AC drain pan, and then into the AC condensate drain line. This is a PVC pipe which drains to the outside of your home. It may be visible in a crawl space or attic but may also be underneath the concrete floor of your basement.

Your AC drainpipe can become clogged with mold and mildew that forms in standing water within the AC condensate drain pan. A clog may also be due to general dust, dirt, dander, or debris entering the drain line. It could even be caused by a spider building a web!

Clogged air conditioner drain line symptoms are the same whether you have a central air conditioner or a heat pump.  They include:

• Puddles of water near the indoor unit
• Water damage near the indoor unit, including rust on the bottom of the unit
• Musty smell when the AC is running
• Heat pump/AC not cooling house
• Heat pump/AC not turning on

The last two symptoms can be caused by a lot of different problems, so the best thing to do is to call an HVAC professional to sort it all out and get your home cool again.

If your AC drain line is clogged the issue is water leaking and potentially causing water damage to the home, the efficiency of the system is not affected. Some homes may have a drain pan condensate safety switch that will automatically shut down the indoor unit if the water level inside the drain pan begins to rise, to help prevent water damage from a clog. 

But, if your system doesn’t have this safety switch, it will continue running with a clogged drain line. The water will eventually fill up the drain pan and begin to spill out. This water overflow could cause ceiling or drywall damage depending on where your unit is located.

If your air conditioner isn’t working, it’s always safest to have an HVAC professional fix the problem instead of trying to troubleshoot it yourself. This is especially true if your unit is under warranty. Going the DIY route could void your warranty and could potentially damage the system.

As soon as you notice a problem, turn off your air conditioner at the thermostat or circuit breaker box and call for AC repair. When a technician comes to assess the situation, they will likely start by checking the drip pan for any excess water build-up, and clean it out with a towel or wet vac. 

Next, they’ll move on to the actual drain line. To unclog a condensate drain line, the HVAC technician will use a vacuum, wet-dry vacuum, garden hose, or simple snake to remove the clog. When the HVAC technician unclogs your drain line, they should pull out a lump of, essentially, gunk that was causing the clog.

Once the blockage has been removed, the technician will clean the drain line with a mixture of AC drain line cleaner and water. Before they leave, they’ll test the drain line and run your air conditioner or heat pump to ensure the problem is resolved. 

They may also do further HVAC system troubleshooting if they believe you have any additional issues with your cooling system.

An important part of keeping your air conditioning unit or heat pump running is keeping your AC drain line clear, which can be done with regular maintenance. Schedule professional air conditioner maintenance every spring.

During these routine visits, your technician will inspect and clean air conditioner parts. This includes the condensate pan and condensate drain line. When an HVAC technician visits your home, they will clean the drip pan and check it for any leaks or water build-up. Plus, they’ll use traditional PVC pipe cleaner on the drain line to help prevent any potential clogs.

If your AC drain line keeps clogging, ask your HVAC technician to show you how to pour a cup of distilled vinegar down the AC drain line to help prevent clogs. Additionally, keeping both your outdoor and indoor HVAC units free of debris, on and around the unit, will help prevent drain line clogging.

Anne Fonda, Content Writer at Trane Technologies

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Mark Woodruff, Senior Product Manager, Ducted Outdoor

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