I started a new thread because the other one got a bit messy.
I need to tap into a 3 inch pvc pipe (drain pipe) to add two drains to it. One will be for the bathroom sink and one will be a bar sink. I found a 3 x 3 x 2 x 2 tee that might work for this job. I was thinking however that it should be a 3 x 3 x 1 1/2" x 1 1/2". Is there a pvc pipe made with those dimensions?
I plan on adding the tee about 18" inches off the floor. Is this the correct way to do this. I have included a photo.

Hi johnny...

You can always reduce that 3"x3"x2"x2" tee using 2"x1.5" P.V.C. bushings.. ok?

The 18" height is pretty much a maximum height for your applications...so if you have any distance to cover you want to keep that in mind. Here, waste lines require 1/4" pitch per foot of pipe... so need to include that when figuring where to cut that fitting in on the waste stack.

Now... how are you venting the bar sink and the vanity... hmmm..?

Ho wabout that pipe on the left? I am thinking you could add a sink drain here and add the bar sink to the 3"... hard to explain now, but will later depending on your replies...

MARK

I think that draining the sink into the 2" pipe on the left will work. I plan on putting in a vent made by oatey on top.
Then for the bar sink, I could cut into the three inch stack on the right. I am uncertain as how to put the new section with the inlet for the drain. Once I cut the piece out, how do I slide the new section in? I would imagine that there is not too much play in the pipe even with a piece cut out. I plan on using another oatey vent underneath the bar sink. What do you think?
Thank you guys in advance for all your help

Hi John:

Now that I look at it again... I'm thinking you should cut that 3x3x2x2 dbl. sanitary tee fitting right into the stack as you originally planned and reduce the 2" as I mentioned, using the 2"x1.5" PVC bushings. I was so focused on the waste stack and venting issues that I missed where you had the water pipes... ;)

Here's how you install the fitting into the stack:

You prime/cement 3" or 4" pieces of pipe into each end of the double tee fitting and then you measure the overall length of the fitting with pipes installed... let's say it is 11" for now.

Then you will mark out 11.5" on the stack so that the fitting is centered at 18"...see picture. You add the extra 1/2" to accommodate a less than perfect cut and to accommodate the 1/8" RIB on the inside of the clamps you will be using.

Now you will install 2 husky 4 band no-hub clamps (see picture... available only at a plumbing supply house) onto the fitting with pipes sticking out. You start by installing the rubber sleeves onto the fitting with pipe ends and then FLIP the rubbers back on themselves. Slide the SS clamps over the pipe in wall... one on bottom, one on top... tighten the one on top up about 12" for now.

Then slide the fitting with rubber sleeves into place and UNFLIP the rubber sleeves to join the PVC pipe. Slide the clamps down onto the rubber sleeves and tighten them up evenly to at least hand-tight or more.

OK..then install the bushings and then install a 1.5" street 90 right into the left side of the fitting pointing out for the sink. You will install the AAV UNDER THE SINK where it is accessible for the future in case it fails. Sounds silly, but don't foget the PTRAP at finish... ;)

Then run the 1.5" pipe over to the bar sink, and use a 1.5" long sweep 90 when you turn the corner to pick up the sink... this is code requirement. Then install the AAV under the bar sink (as you mentioned) so it can be changed out in the future if needed, and again, install PTRAP at finish.

That should get you gong here... ;)

Let me know if you have more questions...

MARK

Mark:
This is a great explanation of how to tap into the drain stack. This is exactly what I will need to do for my project in the near future. Thanks for taking the time to explain these techniques in such detail (and with illustrations)!

I'm glad you found it studioman... just be sure to SUPPORT the stack if you intend to cut into it. In the case above, I would still support the stack, but with most PVC stacks weight is not major issue, but still need to be prepared just in case.

If cutting into cast iron stack then supporting the stack with a RISER CLAMP (sold at all plumbing supply houses... see pictures) is the way to go. Here, you install the riser clamp, install 2"x4" studs under each side of the clamp and then cut into stack (see picture), etc. If the stack is heavy enough (has multiple floors) then it may be smart to double up on the 2"x4"s... just in case!

;) Pop back if/when you have questions.

MARK