Yes you can, but there may be an easier way. Check with your local laws and see if you can use a wall vent. It works just as good as your existing roof vent, but without all the work of tearing out walls and punching a hole in your roof. to install it you use either a "t" in your waste line and put the vent as far up the wall as possible. 4 to 6 inches is enough but the higher the better. The valve is one way only and will not let smells out but can pull in the needed air to make the drain work properly.