Hi Jj...

What are you connecting here? What size is the vent that goes out the side of the building?
Basically, we need lots more information to give a reasonable answer, OK?

Mark

4" cast iron comes in from the rain gutter to sewer and has a 4" cast vent that exits the building out the side of the foundation.I need to vent a 1 1/2 pvc for a basement bath.getting to the roof is a problem.do you have any suggestions on where to locate a vent satck through the first floor to exit out roof?interior walls are too narrow and was considering exposed in a closet.

Hi JJ

I would expose it in the right or left FRONT of the closet corner... most likely will never be seen tucked over like this.

Also, note here that if you are venting an entire bathroom or even just a toilet and sink the minimum vent size in 95% of the United States is going to be a 2" pipe... ;)

Questions? Let me know, OK?

Mark