Looking to add a bar sink. There is already an existing DWV stack that I believe is dedicated for this (based on location and model homes, etc). This is a diagram of what I'm working with and the fittings I was planning on using (0 is the sink where the P-trap will go horizontal to the back wall)

enter image description here

  1. 90 degree long sweep along the horizontal plane
  2. 45 degree elbow
  3. 45 degree elbow
  4. 1.5"/1.5"/1.5" sanitary tee
  5. 90 degree 1.5" vent elbow
  6. 1.5"/1.5"/1.5" sanitary tee
  7. 2"(bottom)/1.5"/1.5" combo wye

Does this look right? Is there such thing as #7? (seems like most of the combo wye I've found are 2" top bottom). If not, what would be the best way to go from the 2" at #7 to the 1.5" at #6?

Also, if I install a P-trap with a union coupling at #0, that would allow me to take the P-trap off. Would that be sufficient as far as a cleanout is concerned? I'd like to avoid putting a cleanout cover in the wall if at all possible.

2 Answers 2


Since it is a vent to waste transition and not a waste to waste transition -- I would consider a 1.5" to 2" reducer fitting atop a 1.5"/2" combo wye acceptable (the vent line doesn't care).

  • Would/should I use a PVC solvent welded connection or can I get away with one of the flexible PVC couplings (The rubber ones with the mechanical fasteners). How hard is is to splice in 6 and 7 with regular solvent weld joints? Did the rest of the parts seem right? Jul 12, 2016 at 5:01

The sink should be vented right at the sink with a vertical run up and then over to the vent.

#4 cannot be a sanitary tee. It is supposed to be vertical.

Your transition to the vent at position #4 is too far down the drain.

If it is only a bar sink I would install an air admittance valve on the trap arm and run the 2" all the way to the trap arm. Then you can forget the vent connection all together. You shouldn't have any problems however local codes may not allow an AAV valve so check that out first.

Edit: Looking at that again I don't think you can tie the vent in at #6 if that is a drain from up above. I am not a plumber but I believe the vents have to be tied in 6" above the flood rim of the highest fixture. The vent sanitary tees are supposed to run upside down from the drains so they allow the passage of vapor upwards.

Good luck!

  • I agree, an air admittance valve seems like the easiest way to do this correctly.
    – Hank
    Jul 12, 2016 at 15:59
  • According to the NSPC Table 906.1, vents can be located within 6' of the fixture trap for 1.5" DWV lines. The sanitary tee will not be horizontal - rather, the "middle finger" will not be horizontal, but rather vertical. Jul 12, 2016 at 17:23
  • If that is 6' or less then you are set with that part. Check back to the other lthread and look at the picture of the sanitary tee I posted, the "middle finger" as you call it can ONLY point horizontal. The straight through part needs to be vertical. You will have to use a sweep tee or the combination of a wye and a 45° at position #4. Again, you can't connect a vent to the vertical if it is being used as a drain stack from above, this will allow drain water into the vent. You have to go up until you are 6" above the flood rim of the highest fixture.
    – ArchonOSX
    Jul 15, 2016 at 1:29

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