I have a couple of questions about plumbing drain / vent layout in a basement

a. do any of the attached diagrams work, and is one superior to another?

b. Can the toilet vent be 2" or does it have to be 3"? The plumbing code I have suggessts that it can be 2" but other places suggest that it should be the same size as the required drain

3. is a closet bend required under a toilet or can it drop directly to the drain?

Under UPC I would rough it in as pictured. You can combine toilet vent and the sink vents into one and continue through the roof with one 2" pipe. Milo

Thanks! Is there a reason that your diagram shows the shower vent joining the lav vent rather than the toilet vent? The toilet vent is a dry vent and would join the lav vent in the attic space above

Thanks again

Archsoln

Good question: there is no reason for it. That's just the way I drew it. But yes, you can combine these vents any way want. Milo

Thanks again. A follow up if you don't mind. I understand codes restrict the vertical riser under a toilet to drop 24" max before turning, Does the code specify a 90 deg. Turn, or is a 45 deg, bend into a wye on the waste stack acceptable?

I am not aware of 24" drop requirement. We did jobs on slab where drops were deeper and with no problem. Now I understand, if you have toilet on 2nd floor you don't want water to drop too deep since it would be way too noisy for occupants below. That can be solved by off-setting the drop with couple of 45 degree turns.

As far as waste transitions go: from vertical to horizontal, we use Y and street 45 degree bends glued together. Same for horizontal installation.

Hope that helps. Milo