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Thread: A/C overflow

  1. #1

    Default A/C overflow

    My airconditioner is draining into the secondary overflow pipe. What could be causing the system to not use the primary?

  2. #2
    DIY Senior Member Mikebarone's Avatar
    Join Date
    Feb 2006
    Phoenix, AZ

    Default Drain line

    Your primary line is probably clogged up with debris. If you want to try it, you can take off one of the side panels on the unit, and see whatís blocking the drain line. Make sure you turn off the unit first. You can use a shop vac to blow out the line (from the outside), but I would first try and blow the clog up to the unit, so you donít lodge the debris into the line, by sucking it at first.
    Make sure you take care of this problem as soon as you can, because if the second line gets clogged up the water will over flow and soak your drywall, (if your unit is in the attic).


  3. #3

    Default One more question

    I just noticed that the primary overflow is dripping. It seems that the secondary drips when the unit has been on for a long time. Any other thoughts?

    Thank you!

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    The main line may not be totally blocked, and on a humid day, the overflow makes it to the secondary...still think you need to clean out the drain line. Normally, if the main line is running free, it can handle all of the condensate.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5


    You need to clean out the line pronto. You can use a little snake from the inside or the outside. You can also use compressed air. If working from the outside end, watch out for the deluge when you finally break through the blockage. That water can be very foul-smelling.

    If using compressed gas, don't ever let go of the hose, or you can really hurt yourself.

    They also make tablets that you can put in the drain pan to help dissolve mineral deposits.


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