Hey Tom, hope all is well.
I am now doing a full remodel on our main bathroom. Our main drain is 3" and I would like to have the main stack come off of that at 2". This vent will serve a Toilet, and tub. I would like to run this vent up through the wall into the attic where I will transition it into 3" pvc where another 2" vent from our basement bathroom, and a 1 1/2 vent from a lav, and a 1 1/2 vent from a shower will all meet up before exiting the roof as 3" Pvc. Is this acceptable? Thank you.
Mike

Hi MikeCT05

Tom's computer is down for a couple days so I'll have to field this question for him, OK?

Here, everything you presented seems reasonable EXCEPT that you must run at least (1) 3" full-size vent from the basement all the way up and through the roof to meet code requirements.

You cannot take a 2" vent and another 2" vent and combine them into a single 3" vent to meet the requirement. You MUST start 3" (or 4" if your main drain is 4") in the basement and continue that vent undiminished in size until you go out the roof. The other 2" vent can certainly connect into this 3" vent before it penetrates the roof.

If you would care to discuss this more just let me know, OK?

Glad to help! Mark

Hey thank you very much, That does pose a problem for me on how to hide this 3" pipe up through the first floor bathroom but I guess I will have to make it work.

I do have two questions about the toilet install. First of all is a closet bend just a 90, or is it something special? and secondly I am running my 3" pipe from the toilet between joists and would like to know how to add a cleanout to this. Can I just have a Sanitee act as the closet bend with the back part a cleanout? Or is there some other better way to do this? Thanks again!

A closet bend can be described as a 4"x3" elbow (3" pipe increasing to 4" at the toilet to accept a 4" closet flange)...see image, but most of the time we just use regular pattern 90s for toilet bends.

In terms of a cleanout, you don't need anything under the floor, but you can install one at the base of the 3" vent stack. Here, you could use a sanitary tee with a cleanout but you will really be better off installing a TEST TEE cleanout (also called a dandy cleanout) in the vent stack... see image.

Mark

So this Test Tee is installed on the vertical run of the vent stack? Thank you Mark

Actually, this cleanout is usually installed at the base of the WASTE stack... then the waste stack turns into the vent stack once all the fixtures have been picked up... make sense?

If this was a basement bathroom we would install a test tee cleanout on each pipe coming out of the floor AND at the base of the waste stack.

Above ground, these are usually only installed under sinks and in tub and washer vents if you want to gain access to the drains without having to snake through the PTRAPS of the fixtures in the future.

Hey Mark, thanks again for all your help. Sorry to get back to this thread, but I have had some conflicting info concerning this topic.

I was told that here in CT we are under the IPC and that it once was code to do just as you said, however under the new IPC I no longer need to have a vent the same size and going directly from my main drain line. Well I will try to look it up myself now, but if you are sure of needing the 3" please let me know.