so I found a leak from my drain pipe inside the wall and the source of the leak is from a broken sanitary tee that connects the 2" vent from up top, horizontal 1.5" drain pipe from sink, and 2" drain going underground. How would I go about fixing this? Make 3 cuts to remove tee and cut small sections of pipe and use couplers to join with new tee ?enter image description here

Thank you guys for all the tips and suggestions. I was able to get most of the fittings/pipe dry fitted. I bored out that hole in the stud just a smidge so there's some play between the T and the horizontal pipe. Just need to make a connection to the vent. Might have to use a flexible coupling. Few questions I have does the pipe have to be pushed all the way into the coupling until it reaches the little stop? I can get it in maybe 5/8 of the way and I measured it's about 7/8 to get to the stop. Also do I need to get this inspected once I'm done?

enter image description here

  • 2
    Are you able to slide the vent pipe upward at all? In a perfect world that just shoots through the roof with no attachment. Otherwise, look for a slip coupling that has no stop. This is why I suggested that you have a solid plan (it looks like you're cementing things already, and not in the order I listed). Typically, small repairs like this don't call for a permit or inspection.
    – isherwood
    Jul 21, 2020 at 12:55
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    I haven't cemented anything just dry fitted. I can't push the vent upward at all no play whatsoever. I tried looking for a slip coupling but couldn't find anything at the local store. I got a fernco fitting with the two metal clamps on each end but I wonder if it can be used to seal off sewer gas.
    – Striplerx
    Jul 21, 2020 at 16:18
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    Shielded Fernco couplings are allowed, but I'd make a slip-coupler by grinding out the stop on a standard coupler with a Dremel or other rasp. Just mark the pipes so you can get it centered.
    – isherwood
    Jul 21, 2020 at 16:24

2 Answers 2


You've got it! Make sure that you

  • use matching black ABS pipe, not white PVC
  • get glue appropriate for ABS, not PVC
  • make sure you clean off the drain pipe so the glue will adhere properly
  • since you've got a fair bit of room to work, cut your straight pipes far enough back that you can easily work with them
    • do not try cut right at the edge of the T, your life will be miserable.
    • I'd suggest cutting the drain just enough up from the sole plate that you can slip the coupler on with a bit of room to spare.
    • Cut the horizontal about mid-way between the studs
    • Cut the vent high enough that you've got room to work, but not too close to the extra stud - it might interfere with getting the coupling on.

You might need to use a flexible coupling to get the T reinstalled since you've got to get all 3 in at the same time. OTOH, there may be enough flexibility in the vent stack that you can wiggle it together without one - you may have to play with it as you're dry fitting everything to find out.


Yes, you'll simply cut all three pipes back a ways and rebuild using couplers, as you suggested. I would do the vertical joints first, cementing them all at once so you can twist them well during assembly. You should then be able to flex it leftward enough to get the drain parts in place. However you go about it, have a plan. Cemented parts don't come apart after about a minute.

Note that the tee probably failed due to stress. Unless it's a trick of the light, there appears to be a slight angle to it, possibly due to being torqued or pulled by the incoming drain line. Be sure all your parts fit comfortably before and during cementing.

  • 1
    good catch on that flex! It does look like the horizontal run was cut a smidge too short and the pipe "flexed to fit".
    – FreeMan
    Jul 20, 2020 at 14:41
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    Yes it does seem a little stressed against the stud where the 1.5" horizontal connects. It's pressed tight right against that hole in the stud.
    – Striplerx
    Jul 20, 2020 at 14:43
  • Document this and attempt to get the plumbing contractor who did this work to pay for repairs. Jul 20, 2020 at 15:53

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