Cleaning out a blocked AC condensate drain line

When most people think about their air conditioner, they don’t think about water. That’s because your air conditioner—which produces water as a byproduct of the refrigeration process—is able to quickly and quietly drain it out to your yard. However, when your AC drain line becomes blocked and is unable to properly drain moisture, your AC will likely stop working and you’ll need to call Wagner for AC repair.

In this article, we’ll review what the AC condensate drain line is, what can cause it to become clogged, and how—if you’re in a situation where your AC has stopped working—you should go about fixing the problem.

What is an AC condensate drain line?

As your air conditioner pulls in hot air from your home and starts to cool it through the refrigeration process, that hot air releases any humidity it’s holding at that time. This humidity forms liquid water that must then be moved away from the AC unit inside your home. This is the job of the AC condensate drain line. This pipe—typically made of PVC—runs from the AC air handler out to the side of your home, typically draining water out into the yard outside.

The AC condensate drain line is related to its drip pan. Located beneath the air handler, the drip pan helps to collect any excess moisture coming from the system, as well as serve as a backup for the drain line in the event that it clogs. Without the drip pan, the ceiling beneath your attic air handler would probably start to get routinely damp in the hot, humid summer months.

How do I know if my AC drain line has clogged?

A clogged drain line is a major problem—and a potential safety hazard. A rapidly filling drip pan can not only spill over and damage wood and drywall around it, but it can potentially submerge wires and other electrical components, damaging your air conditioner.

To prevent this from happening, most modern air conditioners feature an AC float switch. Located in the drain line near your air handler, this component senses when there’s a clog in your drain line, as the rising water causes the switch to float up—much like the float in your toilet stops water from filling the tank past a certain point. When the float switch triggers, it cuts power to the AC unit. This accomplishes two things: first, it prevents the AC unit from creating more moisture through the refrigeration cycle, so that the problem doesn’t get worse. Second, it ensures that if the drip pan does overflow, there won’t be live electrical components for the water to come into contact with.

Unsurprisingly, most homeowners aren’t keeping a regular eye on their drip pan in their attic. In most cases, you’ll know your AC condensate line is clogged when your AC stops running. If you have a smart thermostat, you will likely see it display a code indicating that the air handler has no power. While this error could be potentially caused by another problem with the system, it’s pretty likely that the condensate line is the issue.

One potential sign that your AC line is clogged? If your AC keeps losing power and then regaining it about 30-60 minutes later. This happens when you have a partial clog. As the AC stops running, the water is able to slowly move through the pipe to the point where the float switch lowers back into its normal position. Then, the AC starts up again until the point where the float switch triggers.

If your attic and air handler are accessible and you feel comfortable checking it out, look at the system and the drip pan to see if you notice any standing water. If you do, relay this information to your Wagner technician as they’re on their way out to your home—it’ll make diagnosing this problem easier.

Why causes the AC drain line to clog?

Here in Albuquerque and the U.S. Southwest, our AC drain lines tend to clog more often than those in other states due to the high amount of dust in the air. As this dust moves into your attic, some of it gets sucked into the open end of the drain line. When it comes into contact with moisture, this dust can start to become more solid, sticking to the interior walls of the PVC pipe and starting to form a clog.

On the hottest and most humid days of late summer, even a partial clog can be enough to back up the line and trigger the AC float switch, shutting down the AC unit. The more humid it is, the more moisture needs to flow through your condensate line to properly drain the system. It’s why most clogs start out small and aren’t really noticed until the humidity picks up.

Dust isn’t the only culprit. This line can also become clogged due to insects, small pieces of insulation and other physical blockages. It’s less common here than it is in the Southeastern United States, but it’s even possible for algae or mold to grow inside of the AC drain line.

Related: What is the strange smell coming from the drain line?

How to clean out an AC drain line

If your AC has stopped working, you’re probably going to want to bring in one of our techs to help you out. Most AC lines clog on the hottest and most humid days of the year—not exactly a great time to be doing work in your attic. Plus, HVAC technicians have access to specialized tools to help clear the line. This includes both portable air compressors / tanks (for blowing out the line and expelling the obstruction through the bottom) and small wet-dry vacs for vacuuming out the line. They’ll even use some tools from the plumbing side of the house—such as snake tools—to try to clear the blockage.

One tool that most homeowners don’t have access to, but can be incredibly helpful for AC drain line cleaning, is a compressed air gun. This device uses CO2 cartridges to “fire” a strong blast of compressed air down the PVC pipe. You’ll often hear HVAC experts and plumbers refer to this as “blowing out the line.” Although recent supply chain issues have made these “guns” harder to come by, many HVAC techs still use them to clear out the toughest of blackages and get your AC running again.

Related: Do you need to call a plumber or can you DIY your clog?

Watch: See how to clean out and maintain your AC condensate drain

This video shows the process for cleaning out an AC condensate drain.

Call Wagner for help with your AC drip line

If your air conditioner has stopped working, you’ll want to call your friends at Wagner for AC drain cleaning. We’ll help diagnose the problem and—if it turns out to be your AC condensate line—we’ll work to resolve it quickly and cleanly. Once we’ve cleared out the drain line, your AC should continue functioning normally, allowing your home to quickly cool back down.