I have a mini split in a bedroom that was set up so the condensed water drains via a plastic hose into 5 gallon bucket in the cellar. There is no proper drainage in the cellar so periodically I have to carry the bucket up the stairs and dump it out.

This is getting old fast especially when someone in the house leaves the window open with the AC on! Grr.

Would it be possible to drain the water into the soil pipe instead? Adjacent to the bucket is the soil pipe with a trap and jim caps similar to photo below.

Perhaps I could replace the cap on the house side with, say, a 2 foot tall pipe and fit the hose into that? I'm thinking it needs a length of pipe so backups don't overflow -- I've seen something similar in use in clothes washers in basements I believe.

soil pipe with clean out

Edit to add: The mini split is in a bedroom on the ground floor, one floor above the cellar. The mini split is mounted on an interior wall and there is not easy route to the outside.

Suggestions for other approaches are most welcome.

  • Is this bedroom in the basement or is it a floor above? The air handler for a minisplit should be high enough on the wall that you could direct the condensate line out an exterior wall and let it drip onto the soil outside. Modifying the main sewer clean-out to accept condensate from a minisplit (or even a standard split) seems a bad bargain. For one thing there is supposed to be an air gap for anything from the living space going into a sewer, and you would need a trap. Commented Aug 14, 2018 at 19:18

2 Answers 2


Are you against installing a sump basin in the cellar and having the split drain into that, with a sump pump to push the water outside of the house? Maybe this is financially prohibitive, but I suspect you could DIY it relatively inexpensively.

That said, I'm not a plumber, but you could optionally add a 45-degree branch, shaped like the pic below, extending up from the "house-side" cleanout access. In your case, I would keep the vertical run capped, basically just extending the existing clean out upward a couple feet, and drain the mini-split into the 45-degree branch.

.......there are some caveats, for which a plumber's experience would be desirable:

1) What happens if/when you have a backup? Where does that problem manifest itself?? It should backup into the next lowest point, which is probably a bathtub, but the mini-split will be introduced as an option!

2) Venting. The dripping from the split probably doesn't need a vent to flow, but you might acquire a sewer smell in that bedroom. This might even be illegal in some respects, like if the home or room is rented.

3) You might hear gurgling sounds in that room, as water flowing through the piping will be transmitted up to the evap/fan assembly. Washing machines draining, toilets flushing, and bathtubs draining might be enough flow to transmit the gurgling sounds.

I would advise the sump basin/pump strategy, but the above could probably suffice as a short-term solution in the meantime. Again, I'm not a plumber!

enter image description here

  • Thanks! The bucket actually sits in the sump basin where the sump pump used to be, but it was inoperative ever since we lived here. IIRC it pumped into the clean out opening. Will leave this unaccepted for now to see if others have alternate suggestions.
    – AllInOne
    Commented Aug 14, 2018 at 16:16
  • Yep! I agree with leaving unaccepted to encourage other ideas!
    – elrobis
    Commented Aug 14, 2018 at 17:05
  • 1
    Finally go this handled a couple of weeks ago. Your advice was really valuable. I'll post a photo as my own "answer" when I can get around to it. Thanks!
    – AllInOne
    Commented Oct 7, 2019 at 13:29

If there is a water trap to prevent sewer gas coming in the house I don't see any real problem if the drain is sealed the mini should be well above your sink and bathtub drains so it would not back up to the unit. The only problem I could foresee is when a toilet is flushed the pressure might push a little of the condensate back up the tube. A check valve at a easy to get to location would eliminate the pressure back up problem but I doubt it would be much at all and it would go back down the drain.

  • One potential problem is evaporation from the trap over time. If this is left open, the water level could drop significantly enough to allow for gasses to vent through.
    – Hari
    Commented Aug 14, 2018 at 19:27
  • 1
    If the unit is running or water is used in the home the trap will be filled. It would be more likely for a floor drain trap to dry up in this case.
    – Ed Beal
    Commented Aug 14, 2018 at 19:31
  • I agree that it should normally be filled, but it's a potential problem. Also, as the second trap in any system (the first being at the fixture), hopefully it would clear sewage and only ever be filled with clean water, but I doubt that would be the case. As such, it would be similar to having an open sewer line in the house.
    – Hari
    Commented Aug 14, 2018 at 19:33
  • A check valve would slove any back up of water or gas as I said in the answer.
    – Ed Beal
    Commented Aug 14, 2018 at 20:35
  • My bad, I think I interpreted that to mean a check valve on the drain from the house not the condensate line. I also inferred that you meant leaving the cleanout open with the condensate line above it dripping into it (with an airgap).
    – Hari
    Commented Aug 14, 2018 at 20:53

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