I have a full bathroom in the basement and the sink and shower drains have a trap. Last year I hired a contractor to finish the basement. I wanted to have a bar sink installed so the plumbers installed a drain pipe along a wall, jack hammered up the basement floor and connected the pipe to the main sewer drain. The main sewer line is located below the basement floor. What is the significance of this? The lid to gain access to the main sewer line is located in a closet. I enclosed this section of the basement to hide the lid and the main water lines that enter the house and the drain pipe for the bar sink. The odor is coming from this closet area. The smell is not strong around the lid or pipes. The air in the closet is just a gassy smell.
I do not think I have a moisture problem?? I let the basement sit for 3 years before I had it finished. I never saw any water or damp spots. But just because I did not see any water I know I could still have moist air entering my basement. My basement walls were sealed on the outside when the house was built. The basement floor is now covered with ceramic tile and carpet. How would I know if moisture was actually my problem?