My overflow drain has gas

[outtafocus]

Update: I wasnt happy with my pervious contraption so I set out to build a Durso. This proved to be a fun task seeing as my overflow box is only 4"x4", a standard T and street90ell would not fit.
I basically had to cut the 90 almost in half and remove the enitre middle spout from the T, so it looked like a coupler with a flatened hole in the middle. I then sanded both cuts as square as I could make them. They were ready to go so I used my PVC cement to bond the pieces together. I figured this was where my plan would fail because there was nothing to support the 90 on the T. Well the cement held the 2 pieces together and it is an amazingly strong joint.

This Durso is far superior to my modified stockman. No rise/fall, good flow and even quieter than I had it before. I knew going in that I may have problems with using 1" pvc with a 1" bulkhead (Durso recomends 1 1/4" pvc reduced to the 1" bulkhead) but all seems to be running good.