ABC Blog

Why Does My AC Drain Line Keep Clogging?

a home with a clogged ac drain line

When your AC drain line keeps clogging, it can be frustrating if you don’t know why it’s happening or how to resolve it. Even worse, a clog in the line can lead to even bigger AC problems that require expensive repairs. Fortunately, a clogged condensate drain pipe is a common issue that usually isn’t too complicated to fix. It’s even easier to take some common-sense steps to prevent the line from clogging in the first place.

Here are some signs that your AC drain line is clogged:

  • There is standing water in the drain pan of the AC’s indoor unit.
  • There are damp conditions or water damage near the indoor unit.
  • A moldy, mildew-y or musty smell is coming from the indoor unit or from the AC vents in the house.
  • The AC isn’t working—either it won’t turn on, it shuts off unexpectedly, or it runs but isn’t cooling the home.

One common reason why AC drain lines get clogged is because of mold growth. This can happen occasionally in any home because the AC drain line stays humid. The line conducts water from the indoor unit to the outside of the house. Warm air from the AC combines with the damp conditions to create the perfect conditions for algae to grow.

Another common cause of clogged AC drain lines is excess dust or debris in the AC system. Dirty AC filters and coils can allow dust to get into the drain line. Periodically flushing the drain line with water can help keep the line clean. Flushing with vinegar or bleach will also help keep algae from growing inside the line.

Some experienced DIY homeowners can flush the drain line on their own, but it is better done by a professional as part of a routine AC maintenance check. Signing up for regular AC maintenance is a great way to keep your heating and cooling system running in top condition. An AC specialist can make sure your system is running at peak efficiency and can head off many problems before they turn into costly repairs.

How to Prevent Clogged AC Drain Lines

Most people have AC maintenance checks done in the spring and fall. That way, the inspections can be performed right before the weather heats up or cools down. When the temperature changes at the start of a new season, it puts new strain on the AC system. A heating and cooling professional can inspect your entire system, including indoor and outdoor units and all connected ducts, pipes and drain lines, to ensure everything is in good working order.

In between scheduled maintenance visits by your AC specialist, there are things you can do to help keep your heating and cooling system in good working condition. The following steps will help to avoid problems like a clogged drain line.

How To Prevent Drain Line Clogs

Clean or change your AC filters frequently. You should change the filter about once every three months. In homes with furry pets or higher amounts of dust or pollen, the filters need changing even more often. This will keep dust out of the system and help the AC to continue working efficiently.

Check your AC drain pan and drain line regularly to make sure they are functioning properly. The drain pan should be dry and clear of debris. The drain line should look and smell clean, and the water coming out of it should be clear. You may see a thin trickle or drip of water coming out of the drain line outside the house. If so, this is normal. When the water backs up in the drain pan because it can’t get through the line, that’s when it’s time to contact an AC specialist for help.

Schedule regular AC maintenance with a licensed and reputable professional. Regular maintenance is best conducted twice a year, in spring and fall. This maintenance should include a system-wide inspection and cleaning. The AC specialist should look at the units both indoors and outside, and should clean both. They should test the coolant levels and the thermostat to make sure the system is working correctly. They should also inspect the ductwork for leaks and the registers for airflow.

The best way to extend the life of your AC is by hiring a professional for regular maintenance. This will also save you money by preventing costly repairs that can result from ignoring AC issues as they start to develop.

an air conditioning unit

How Does AC Work?

Most homeowners don’t wonder about their air conditioning system until it breaks down. Then it’s common to wonder or ask your AC repairperson, “How does AC work?” Your AC is a complicated system with many interconnected parts. Understanding how it works can help you understand why it’s so important to maintain your heating and cooling system over time.

Central AC systems have indoor units called evaporators that connect to the home’s furnace or air handler. The evaporator is the part of the AC that removes hot air and humidity from inside the home in summer. The evaporator cools the warm air with refrigerant and then pushes the cooled air through the home’s ductwork to every room in the house.

AC systems also have outdoor units called condensers. These units hold the refrigerant as well as a compressor that pumps refrigerant back inside to the evaporator unit. Both the condenser and evaporator units are made up of many different components. These include fans, motors and filters. Any one of these parts can break or wear out over time, especially if the AC is not regularly maintained.

The entire AC system is controlled by the thermostat. Usually mounted in a central spot in the home, the thermostat is where you can turn the AC on and off. The thermostat sets the AC to Heat or Cool, depending on the season. You also use the thermostat to set the temperature you want your home to reach.

As the air inside the home circulates through the coils within the evaporator unit, the moisture in the coils can trap dirt, dust and debris. Some of this debris will move out of the house through the drain line. The rest of it will build up within the system over time. This is what can cause clogs in the AC drain line.

This is why it’s so important to clean or change your AC filters on a regular basis. You should change them at least once every three months. Change them more often if you live in an especially dusty area or if you have pets that shed fur inside the home. Extra fur, dust and dirt in the home leads to extra debris in your AC system, which can lead to clogs and other problems.

Aside from changing out your AC filters regularly, the other important step you can take to keep your AC in good shape is scheduling regular AC maintenance. An AC specialist can head off problems and extend the life of the system. Between maintenance visits, it’s important not to ignore unusual sounds, smells or other symptoms that might indicate you need an AC repair. Taking care of small issues as they arise can help you avoid bigger, more costly repairs.

an HVAC professional maintaining an air conditioning unit

How to Clean AC Drain Line

Knowing how to clean an AC drain line is helpful in preventing clogs from happening. Keeping the drain line clean clears debris and prevents mold from growing. Some experienced do-it-yourself homeowners can handle this job on their own, but most people are better off leaving it to a professional. Cleaning the AC drain line is part of routine AC maintenance. A reputable, licensed AC specialist will include flushing the drain line as part of their regular checklist of to-dos when they service your AC.

When a heating and cooling professional cleans the AC drain line, here are the general steps they will follow:

  • They will turn off the AC unit at the thermostat and also at the breaker, to protect against the possibility of electrical shock.
  • They will find where the drain line comes out of the exterior wall of your home outdoors. It will be a PVC pipe, an inch or so in diameter, that extends all the way from the indoor unit to the outside of your home. The AC pro will inspect the drain line for any signs of algae or debris.
  • They will then head to your indoor unit to inspect the drain pan for standing water and debris, and clean it if needed.
  • They will find the access point on the drain line—an open part of the line that points upward and is covered by a cap—and flush it with water to remove any debris from the line.

The AC specialist might recommend measures like installing a condensate trap, if your AC system doesn’t already have one. They can also recommend the best air filters for your system, to filter as much dust and other tiny particles out of the air as possible. This will help to keep your AC as clean as possible, which in turn will help it continue to function at peak efficiency.

ABC Can Keep Your AC Working Efficiently 

Dealing with AC issues requires lots of technical know-how. Instead of trying to figure it out yourself, contact ABC Home & Commercial Services. Our professionals can efficiently diagnose your AC problem and get to work on fixing it. You can also rely on us for honest advice on when to replace your air conditioner.

Tom Riggs

Tom Riggs is the Division Manager for Mechanical Services, overseeing sales and operations for HVAC, Plumbing, Electrical, Appliance Repair and Water Quality for all ABC Austin branches. He joined ABC in 2014. Before ABC, he was an HVAC Service Technician, HVAC Comfort Advisor/Sales and Operations Manager. Tom attended Universal Technical Institute. He's an avid outdoorsman and enjoys country living with his wife and two sons.

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