Every year, tens of thousands of US homeowners call for professional HVAC repair due to clogged AC drain lines. HVAC companies can charge $50 to $150 per hour or more and that’s on top of their service fee. It’s a lot of money to shell out, but you have no choice.
Or do you?
The truth is that cleaning out a clogged AC drain line is something that most homeowners can handle on their own with a little bit of information and planning. That means you can save time and avoid paying hundreds of dollars for a repair that you can do on your own.
What Is an AC Drain Line?
Air conditioners create a lot of condensation. Moisture accumulates on the evaporator as the unit operates. In very hot, humid conditions, your system can produce up to 20 gallons of water a day! All that moisture must go somewhere but the “where” depends on your specific setup.
In many homes, the primary AC drain line is connected to a drain hub, which is then usually connected to a sink or tub drain, so condensation drains into your home’s sewage system. These types of setups also include a secondary drain line that runs from the evaporator to outside the home. If you notice water dripping from this, it’s an indication that your primary line is blocked and needs to be serviced.
However, not all homes have a setup like this. Instead, the primary drain line runs from the evaporator to the outside of your home and there is no secondary drain line. You’ll see water draining from this when your air conditioning is running, and it is not a cause for concern. Instead, if the AC is running but you don’t see water coming from the drain line, it’s a sign that you have a blockage. This setup is common with mobile homes and in older homes built before today’s building codes.
How Does an AC Condensate Drain Line Work?
AC drain lines aren’t particularly complicated. They’re nothing more than combinations of flexible piping and PVC pipe that allow water to drain from the catch pan on the evaporator to the outside of your home. There are no moving parts and no electricity involved.
That said, some systems do incorporate a condensate pump. If the drain line cannot maintain a negative slope to allow gravity to pull the water out, a condensate pump forces water out through the drain line against gravity.
What Causes a Clogged AC Drain Line?
AC drain lines clog due to a few basic reasons, including:
- Mold
- Algae
- Debris
When any of these build up, they can slow or block the flow of water out of the catch pan, creating a dangerous situation. Once the water fills up the condensate pan, it will spill over, which can affect the AC (short-circuiting, rust, etc.) or damage your home (water damage, mold, growth, wood decay, etc.).
Thankfully, most systems are protected from damage through the auxiliary drain and, in most cases, should have an emergency cut-off switch in place. This switch must be located within sight of the evaporator and should be installed by a licensed HVAC contractor. You should be able to find your switch on the side of the unit or on a nearby wall.
Flipping the switch immediately stops the flow of electricity to the unit for safety. Note that today’s building codes require an emergency shut-off switch to be installed, and most homeowners’ insurance policies also require it.
Where Is the AC Drain Line Located?
You’ll find your drain line attached to the condensate pan on the evaporator unit inside your home. Depending on the location of the unit, you may need to open a closet to locate it, although some homes have the evaporator located in the attic, and some even have them in the garage.
The line runs from the condensate pan under the home and then ties into your home’s plumbing. Your secondary line runs from the condensate pan to the outside of your home. You can usually locate the terminal end of the line near the condenser unit (the large outdoor unit with a fan responsible for dissipating waste heat).
The Importance of Unclogging an AC Drain Line
Regularly unclogging your AC drain line is important for several reasons. As mold, algae, or debris first slow and then clog the line, condensation can no longer flow through the line and out of the home. It begins to back up, first in the line and then in the condensate pan.
Once the condensate pan is full, the water will begin spilling over the sides. This can drip onto the electrical components of the unit, including the blower motor, causing a short circuit. It can also damage the structure of your home.
Water damage can rot flooring and allow mold and mildew to thrive in the structure. Unclogging your AC drain line helps prevent these dangers.
Clogged AC Drain Line Symptoms
Not sure if your AC drain line is clogged or not? Here are a few common symptoms to help you determine the situation. Symptoms of a clogged AC drain line include the following:
- A musty smell near the vents in your home
- Standing water near the indoor unit
- Visible water damage to the walls or floor around the indoor unit
- Water dripping down the indoor unit or dripping from the secondary outdoor drain line
- Water spilling out of the condensate pan on the indoor unit
- Visible mold or algae within the terminal end of the AC drain line
- Your AC system is not cooling your home because the emergency shut-off switch has activated
DIY Methods to Unclog the AC Drain Line
Unclogging an AC drain line is something most homeowners can do. You’ll find a couple of different solutions depending on the severity of the clog.
Flushing the Line
One of the simplest options is to flush your AC drain line with a mixture of vinegar and water, or by adding bleach to the condensate pan. Vinegar is a mild acid that kills both mold and bacteria, and bleach kills both mold and algae. As they die, the mass reduces, and the force of the water pushes the debris out of the line.
Note that if your HVAC system has been in place for some time and you have not flushed it previously, you may notice that shortly after using either bleach or a mixture of water and vinegar, your line becomes clogged. As the mold/algae die, it breaks away from the sides of the drain line and can accumulate downstream in the line, causing a clog.
In this case, you will likely need to contact an HVAC company to unclog the line.
1/4-Inch Sink Cleaner
For very serious clogs, you may need to take more drastic action. You can buy a coiled, 1/4-inch sink cleaner at most big box stores and hardware stores. It rolls up within a case, like a tape measure. However, these are usually only about 20 feet in length, so may not be able to reach your clog.
- Insert the end of the cleaner into the drain line and gently run it out until it encounters the blockage.
- Push it through the blockage and then move it back and forth to scrape away any remaining debris inside the line.
- Flush the line with water to clear it all out.
How the Pros Do It
HVAC professionals have a different way to unclog AC drain lines: compressed nitrogen (an inert gas denser than air). By injecting compressed nitrogen into the drain line, the clog is blown downstream, past the drain hub. Before this is done, however, it’s important to identify the tub or sink the line connects to so that the drain can be covered to prevent water and debris from being forcibly ejected during the process.
How to Prevent AC Drain Line Clogs
Keeping your drain line free of clogs is important, but how do you prevent those blockages? You can pay for professional drain line cleaning from an HVAC company, but chances are good you’ll pay between $100 and $250 per incident. You can clean it yourself and save that money, but a better option is to avoid clogs in the first place, which means maintenance.
You have a couple of options for maintenance. You can go the DIY route and use the vinegar/water mix method or bleach, or you can sign up for twice-yearly maintenance with an HVAC service company.
With an annual HVAC service, your drain line is inspected and cleaned twice a year. That prevents mold, algae, and debris from building up, and ensures that you don’t have to take time out of your busy life to handle drain line cleaning. Plus, it also ensures your HVAC system remains in peak condition for years to come.
