I'm adding a guest room & bath to my basement. This is a raised foundation & the 3" & 2" drains were installed when I built the house. Can I just install a flange & wax seal & install the bowl & for a vanity sink, run directly into 2" or do I need to run a vent pipe.
If so, where where do I hook it in & run it out?

Run 2" vent for toilet and 1 1/2" vent for sink. Combine them about 4' above the floor. Run it upwards to the floor above and connect with existing vents above 4' above that floor. Of course, if you can, run that vent directly to the roof - or to the attic and connect with existing vent there. See the sketch to give you idea how to run them...

In my area we would use the lavatory vent as a wet vent for the toilet (see image). We considerthe extra ventfor the toilet to be just that. A extra vent that we don't need. OIf course if you fall under UPC you run a vent on everything but the family dog. Regards, Tom

Milo & Speedball1 Thank you both