I have a 3" drain running horizontal. I will have a new 2" drain running horizontal to just above the 3" drain at an angle and need to connect them together.

I assume I shouldn't use a regular T here, but should i be using a wye, sanitary tee, long sweep, something else? I'm a little confused on what connector is proper. If I have any options, something that leaves the up spout part as low as possible would be best, as I'm going to be pushing the drain slope requirements as it is.


  • A little more clarity on the sketch, the gray line is the 3"? I would presume that venting is not an issue, and that the water will run from left to right, and your red line is the 2" drain that looks like it might could drop into the 3" line from above as you suggest. Just confirming.
    – Jack
    Nov 8, 2015 at 6:26
  • @Jack Grey is 3", red is 2". Red will be going left to right, grey will be going right to left. Thanks! Nov 8, 2015 at 9:01

1 Answer 1


If trying to join the lines from above the 3" line will cause issues with slope of the 2" line then the thing to do is to do the coupling more from the side of the 3" line. You could cut the 3" line and install a wye fitting with the branch positioned horizontal instead of pointing up. It may be that the branch can even be rotated up a bit from the horizontal side to gain the best fit.

You could then use a size adapter to 2" right off the 3" branch. Then a series of 2" street elbows (22.5 degree elbow) can be used to adapt the direction of the branch to the incoming 2" line.

Using this technique you should be able to get up to about four more inches of slope on the 2" line.

  • It may be needed to keep code that the 3" wye has a slight rotation, so the 2" line coming into it to not allow any backwash from the 3" line. Not much needed, maybe set to the 2 o'clock position, rather than the flat, 3 o'clock position. This also may come naturally to get the 22 1/2 degree elbow to fit anyway.
    – Jack
    Nov 8, 2015 at 17:19
  • @Jack - Yeah I agree. And with several street elbows connected and rotated to various angles it is possible to have a great amount of flexibility in accommodating the incoming 2" line.
    – Michael Karas
    Nov 8, 2015 at 19:18
  • I can't go into the 3" from the side, sadly, because there is a large 4x12 supporting beam next to it. Nov 8, 2015 at 20:55
  • Looks like it needs to be a sanitaty tee with an adapter and a street 90
    – Jack
    Nov 9, 2015 at 1:02

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