You either have to extend the vent pipe higher, or install an AIR ENTRY valve on the top of it. These can be purchased at most good plumbing supply stores. You need one that is the same diameter as your vent pipe. : We have a sewer vent pipe that vents out our roof on the backside of the house.: This, unfortunately is close enough to our newly enlarged deck that anyone on the deck can smell it.: Is there any treatment we can add to the plumbing, or a filter cap we can add to the system?