I added a new addition to my house. In it I want to put a sink and washing machine drain but I don't want to vent them through the roof as it is unsightly and at the front of the house. Can I tie in through the attic to an existing vent that already goes through the roof and still achieve the same ventilation qualities as I would if I went straight up through a new hole without using the existing vent?

What about adding a toilet between that room and the existing main vent?

Thanks, Dan

Can I tie in through the attic to an existing vent that already goes through the roof and still achieve the same ventilation qualities as I would if I went straight up through a new hole without using the existing vent This is called "reventing" and is perfectably acceptable. There is no loss of ventilation when you revent.

What about adding a toilet between that room and the existing main vent?
Works for me. Good luck, Tom