How-To Videos

How to Clean an AC Condensation Drain Line

By: Jodi Marks

In addition to cooling your home, an air conditioner removes moisture from the air to lower the humidity level inside your house. This excess condensed water is removed from the AC unit through a small drain pipe and deposited outside on the ground.

Over time algae, mold, and mildew can build up inside the condensation drain line and form a clog, causing water to back up and overflow inside the air conditioner unit. To prevent this from happening, pour a cup of bleach in the access opening in the drain line near the AC unit to kill any algae, mold, or mildew that has formed in the pipe.

If the condensation line is clogged, you will need to use a shop vac or special pump to remove the clog from the line.

Watch this video to find out more.

Further Information



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15 Comments on “How to Clean an AC Condensation Drain Line”

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  • andy Says:
    August 27th, 2015 at 1:01 pm

    what about if you are on a septic system? boiling water maybe? I just have heard its not good to put much bleach into a tank?

  • Deb Says:
    July 15th, 2015 at 5:58 pm

    How large (what size) wet vac should we buy to clean the a/c condensation pipe?

  • Scott Says:
    October 27th, 2014 at 9:30 pm

    Hello, I. Recently moved into a newly constructed house and found that a substantial amount of air is being blown from the water drain lines coming out of the unit. It is stored in the attic and the attic space is cool upon entry. Is there anything that I can do to keep the air from exiting the line?

  • Kumar Says:
    September 20th, 2011 at 10:16 am

    My house has 2 A/C units.There are 2 pipes running outside the wall (roof level for the first floor and at the floor level of my second floor) where water is dripping slowly. My neighbour scared me saying those are the backup pipes for A/C water drain and the water is never supposed to come out from there. Can you help me understand if that’s true?? My house is 2007 built.

  • Phil Says:
    August 20th, 2011 at 9:11 am

    I have a drain from the A/C to a PVC line that is connected to my bath drain. It was recently unclogged and now when the a/c is on, we hear a flapping sound like a check valve closing. Any idea what it is or how to fix it?

  • Official Comment:

    Ben Erickson Says:
    July 22nd, 2011 at 8:03 am

    Hi Lucy,
    Glad to hear you were able to fix your dripping AC pan, and thanks for following up to let us know how you did it!

  • Lucy Says:
    July 21st, 2011 at 11:25 am

    I want you to know, I fixed the leak in my a/c. I finally broke down and called a plumber and explained the problem. They came out and he took the metal lid off the unit. There was water standing in there. He tried to tell me I needed a new coil. We poured water in to the pan to see if it would drain outside. There was quite a bit of rust and the particles and water slowly started to go down the pipe. He told me to turn the unit off for a couple days and he would be back. I still wasn’t convinced the pipes weren’t clogged. After letting it dry for a couple days, I took the shop vac and blew the pvc pipes and vacuumed out the pan for any remaining rust particles. I sealed the corner of the drain pan with some very duty seleant, turned the unit on and it works perfectly. I think they a/c guy just wanted to make money off me as he told me blowing out the pvc lines wouldn’t work. Bottom line, it pays to do it yourself!

  • mary o'donnell Says:
    July 20th, 2011 at 8:06 pm

    My pvc pipe goes into a box (at this moment the box is full), and then a piece of flexible tubing goes up into the rafter of my basement across the ceiling and down into my laundry tub. How can the water run up? It’s been working fine for five years, but as of this moment water is leaking from the pvc pipe. It’s leaking from where it is connected to the ac unit in my basement. Before the pvc pipe went down and across the floor to my floor drain. Tomorrow I am going to disconnected this box and see what’s up. Any comments/advise would be greatly appreciated. Thanks!!

  • Official Comment:

    Ben Erickson Says:
    July 17th, 2011 at 6:08 pm

    Hi Jim,
    Click on the “special pump” link in the article above, or the “Innovative Pump Unclogs AC Condensation Drain Lines” article link in the Further Information section above, then click on the Mighty Pump link in the article to go to the website of the company that makes it where you can purchase the pump online.

  • Jim O'Sullivan Says:
    July 16th, 2011 at 3:16 pm

    Where can I buy the bicycle type pump for unclogging my AC condensate line?

  • Anna Ramirez Says:
    July 9th, 2011 at 9:02 pm

    My air conditioner is leaking… I got under and vacuumed inside behind the filter, that is where the water was leaking. I attempted clean out the drain pipe with a vacuum and then I poured the bleach down the drain. I hope this works!!!! I will let you know.

  • lucy Says:
    July 9th, 2011 at 12:37 pm

    I’m having water drip from the pan under the unit in the attic. I found the two pvc pipes coming out of the unit along with a copper pipe that has quite a bit of air flowing out around the opening. However, neither one of the pvc pipes have a “T” to open and try and unclog. Any ideas would be greatly appreciated!!

  • larry Says:
    July 3rd, 2011 at 5:42 pm

    Ok. my a/c units drain into a pvc pipe that is tied in to the house’s plumbing. I traced the pipe through the attice and both units go into the large PVC pipe that goes down the wall and up out of the roof to the vent stack. Nowhere to put vacuum to suck out clog. Any suggestions of how to clear clog from the access opening, which has water up to the cap itself.

  • Official Comment:

    Ben Erickson Says:
    August 14th, 2010 at 10:26 am

    Hi Dorothy,
    The port in the air conditioner condensation line in our house didn’t have a cap on it either when we bought it. I bought a cap at a home center for a buck or two to fit the PVC line on my unit, put it on, and it’s worked fine. I don’t think it was that bad not to have one in my case, since the unit was in a closet in the house, but if your unit is in the attic, you’re probably losing some of your cold air out the vent line. Also, it can keep any mice or bugs from crawling into the unit.

  • Dorothy Collins Says:
    August 13th, 2010 at 3:29 pm

    I have a new home 1 year old . I went in the attic to put a cup of bleach in the pipe they showed me when I bought the home. Before they always had cap on the pipe but this dose not. Is that normal? second thing is cold was blowing out the pipe. Is that normal? I would very much appreciat an answer. could you e-mail it to me. thankyou Dorothy

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