Thread: AC Primary drain vent

I have seen several of these lately with tape over the open end. Sorry I dont have a picture, but try to envision the small vertical vent pipe (~ 6" in length) next to the evaporator coil. I skimmed the IRC, but didnt see anything about it.

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Vent should be on opposite side of trap from AHU.

If not, it only serves as a clean out, and allows air to be sucked in or blown out, wasting energy (and, if sucking in, sucks in unfiltered air).

Yes, the vent is downstream of the trap. Im starting to question my understanding of this. I thought the vent was supposed to be open and not taped over or capped. I havent missed some new rule or change in physics have I?

Originally Posted by imported_John Smith

Yes, the vent is downstream of the trap. Im starting to question my understanding of this. I thought the vent was supposed to be open and not taped over or capped. I havent missed some new rule or change in physics have I?

If it is downstream of the trap, it could be a vent, and would be open.

If it is upstream of the trap, it could be a cleanout access, and would be capped.