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How to Clear Clogged Condensate Drain Line

There are three main causes for a leaking air conditioning system: dirty air filter, a damaged drain line or pan, and the much more common clogged condensate drain line.

How to Clear Clogged Condensate Drain Pipe

The first thing you should do is check your air filter and change it if necessary. Then, take a look at your drain pan, located underneath your evaporator coil, for cracks, leaks, or other damage. If it looks like your air filter is clean and your drain pan and drain lines are undamaged, you probably have a clogged condensate drain line that needs to be cleared.

First some basic HVAC information:

Most central air conditioning systems have two main parts: an outdoor compressor/condenser and an indoor evaporator/blower, usually located in the attic but possibly in the basement.

The indoor unit pulls in return air and passes it through the unit’s cold evaporator coil. In the same way that water droplets gather on the outside of your cold drink, condensate droplets will form on your evaporator coils and drip down to your drain pan, located underneath. The water then flows into your condensate drain line (usually PVC piping) and gets carried outside the home, probably near your outdoor unit.

If your evaporator coils are dirty, the dirt, mold, and other contaminants that gather on your coils can run into your drain pan and create a sludge-like substance that clogs up your PVC drain pipe. If you suspect a dirty evaporator coil, call in a professional HVAC technician to clean it, which should be done about once a year. Replacing dirty air filters will definitely help keep your evaporator clean of contaminants.

Now that you know the general workings of your HVAC system, let’s get to the root of the problem:

Clear Your Condensate Drain Line:

If your condensate drain line is clogged, you may begin to notice water gathering around your indoor air handling unit, which is located in the attic, could begin to leak through your ceiling.

As soon as you notice an air conditioning leak, get it fixed right away to avoid expensive repairs and bigger problems down the road. Don’t wait for water damage to your floors and ceilings before you decide to clear the clog. In fact, you should clear your condensate drain line even before you notice a problem, about every year or so.

There are a few different ways to clear your condensate drain line, but the most popular method is using a combination of a wet/dry vac and a chlorine bleach solution. If you don’t have a wet/dry vac, consider purchasing one, or you can check out Mighty Pump, which sells on Amazon for $72.

1. Locate the Condensate Drain Pipe Outside

Air Conditioner Condensate Line Clog


The pipe should look similar to the one shown above.

2. Hook Up Your Wet-Dry Vac

Once you locate your condensate drain pipe, connect your wet-dry vac or Magic Pump. If you can’t hook up your wet-dry vac because the end is too large for the drain pipe, you can buy the proper condensate connection piece from If you want to try to connect your wet-dry vac without the attachment, here’s how the basic setup looks:


3. Turn Your Wet-Dry Vac On

Once you establish an airtight connection, go ahead and turn your wet-dry vac on for about 3 minutes. After you turn it off, you will notice a lot of sludgy crud in your wet-dry bucket:

Wet-Dry Vac


4. Keep Your Condensate Drain Line Clear With Bleach

Another thing you can do to ensure your drain line remains clear is to clean the indoor piping with a strong wire brush and pour a cup of chlorine bleach down the PVC condensate drain pipe. Simply screw the cap back on when you are finished and this should help kill the mold and mildew in your condensate line. Do this every spring before the cooling season begins to help maintain a sludge-free condensate line.


Watch this video for a recap for unclogging your condensate line:

For more tips on maintaining an efficient and working central HVAC system for your Champaign/Urbana/Mahomet area home, read our other HVAC how-to’s:

Call Cassel Home Comfort for a professional HVAC tune-up, condensate line cleaning, evaporator cleaning, and other important maintenance services.

Prevention is the best medicine for HVAC equipment, which translates to more money in your pocket and guarantees that your warranties remain valid.

Call your Home Comfort Experts at (217) 866-1596 for quick, professional service from background-checked and drug-tested technicians.

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