In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
I have two mains which run about 60 feet in a rectangle and risers coming off each one to 3 different floors - one pipe system. I currently have 1 main vent (ventrite # 77) on the end of each main - see picture. Installer says that this is enough venting. Should I have more and are they supposed to be place at the end on a t like that? I was reading that they should be at least 6" from the end of the main. If I need more, where should they be placed. Do I tell him to do the work or hire someone else?