I am in a brand new home of 8 months. When we sit on our deck or by our driveway or even in front of the house, we smell methane gas. We had a smoke test done and it seems that the wind swirls around and comes straight down to give us that horrible smell. What can I do?????
Retired plbg is correct. The drafts around your house are drawing sewer gases from your roof vents down to a level where you can smell them. If you install a U-trap at the point where your building drain goes through the perimeter foundation wall, you will prevent sewer gasses from backing up from the building and municipal sewer pipes into your plumbing vents. However, you will STILL be likely to draw whatever gasses are present in your building drain system vents to where you can smell them on the deck. With a building drain trap, this should be a lot less than without one, however.
Another thing you can do is try to extend the various vent pipes above the roof, to get the gasses to vent upwards rather than get sucked downwards. How much extension is needed will depend on the geometry of your roof. Id’d suggest extending the vents to at least the level of the highest point on the roof.