A sweaty condensation drain line is dripping and causing mold in a ceiling panel:

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The condensation drain pipe is lengthy and spans two rooms:

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Is insulating the pipe an effective means to counter this drip / mold problem? If you have successfully solved this problem please state this in your response and include details / context. Thank you

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2 Answers 2


Yes. Isolating the pipe from moist air has been the common fix for decades.

  • Good. I was contemplating re-routing (re-piping) but it would be easier to insulate, because new piping would require a hole through the building wall.
    – gatorback
    Jul 21, 2017 at 18:09
  • 1
    Make sure you seal the gap in the insulation. If moist air can get in, you'll have condensation inside the insulation.
    – Tester101
    Jul 21, 2017 at 21:59
  • To seal the gap, I am interpreting that that the insulation's slit (gap) must be closed with tape?
    – gatorback
    Jul 22, 2017 at 12:34
  • 1
    Yes. Duct or packaging tape at work well. Some products are self-sealing.
    – isherwood
    Jul 22, 2017 at 12:41

Not sure where you live but in humid climates it is standard practice to insulate condensate drain lines for that very reason.

  • The site is in Florida
    – gatorback
    Oct 21, 2017 at 3:09
  • So just for kicks I looked up the dew point in Tampa. It is currently 69 degrees. Where I am right now the dew point is 42 degrees. The condensation coming off your coil is around 40 degrees and will warm up a little going down the line. Anything below the dew point will likely condense. That is why where you live everyone insulates their condensate drain and where I live almost no one does.
    – user76730
    Oct 22, 2017 at 21:32

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