Softus
Do I need to do this as I aready have a vent running up to the roof from the main stack?
However, capping off the top part is a no-no - it should be connected to a vertical run and carried up to a roof vent, unless the BCO says that you can reduce the height and use an AAV.
Do I need to do this as I aready have a vent running up to the roof from the main stack?