I have a low-pressure condensate drain line where I need to shorten some pvc so that I can create an air gap to the drain. I was going to cut out a PVC section and re-attach with a coupling, but I noticed that the PVC pipes have a streak of whatever concrete stucco-like material was used on the basement walls running the full length of the pipe. This means that I don't have a smooth clean section in the pipe to cement the coupling. Is there a way to shorten that pipe by just pulling it out of the fitting, or would I need to figure out a way to sand the concrete stucco off?

Is there a clean smooth way to remove that stuff... or is there a coupling that goes on the inside of the pipe rather than around the outside of the pipe? Or should I just flex seal tape the thing?

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    this is just a comment, not an answer, but I think (THINK) you might be able to scrape off the stucco, it probably isn't well adhered to the pipe. Sanding would be difficult due to the makeup of stucco. since it's low pressure (probably no pressure), you could use Fernco couplings like the ones below in your pic. Commented Sep 20, 2022 at 11:05
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    Don't adjust the PVC. Just remove the fernco coupling. Boom. Air gap.
    – longneck
    Commented Sep 20, 2022 at 11:17
  • Make an answer out of that, @longneck. You'll get my vote!
    – FreeMan
    Commented Sep 20, 2022 at 11:56
  • Longneck is right, but even if you need to make changes to the PVC, why do you need perfect connections to build an air gap for a drip line? For that matter, why do you need to connect condensate water to a sanitary sewer at all once it's already outdoors?
    – jay613
    Commented Sep 20, 2022 at 13:21
  • "flex seal tape" I should down vote you for even suggesting that! Commented Sep 20, 2022 at 14:25

2 Answers 2


Don't adjust the PVC. Just remove the fernco coupling. Boom. Air gap.


It was never designed with an air gap, so why is one needed now? Drain lines usually are never 100% full so no air gap is needed. If there is an issue, such as they are running slow or not at all, they probably need cleaned out. It is common for drain lines to get algae and other "gunk" in them and need cleaning every few years.

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    An air gap ensures that sewage backflow or sewage gases are dumped near the air gap rather than proceeding up to the HVAC equipment and the room it is in. That may or may not be preferable, but in this case the air gap would be outside so it is certainly preferable.
    – jay613
    Commented Sep 20, 2022 at 13:15
  • Gravity condensate drains almost always need an air gap. Even very little back pressure (e.g. from a downstream trap) will prevent them from flowing. Commented Sep 20, 2022 at 17:37

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