I am remodeling a house I just bought and I am moving the bathroom and expanding the kitchen. I need to move the cast iron main vent 4' to the new common wall between the new expanded area and the new bathroom location. Can I run the vent horizontal for 4' in the basement as long as I install a cleanout cap? Or do I have to move the main vent in the basement concrete floor 4'? Also, can I run two pvc pipes that are equal in area to the original cast iron pipe(from the floor up) so I do not have to build a 6" wall to accept the main vent pipe?