Recently renovated basement. There is access from floor/wall of basement bathroom to street sewage system. All of a sudden, since the renovation, I have a strong methane-like odor clearly coming from that area.

First, was the remodel done by a licensed contractor ? Was there any work done on the existing drain / sewer system ? If positive, was this work performed by licensed plumbing contractor ? Was the work inspected by City Inspector ?

There is number of things that may have not been installed properly during the remodel, like trap & primer missing in floor drain, no trap under shower or tub, open sewer vent, sewer ejector vent missing or not being dedicated vent... and more...

Please, answer the questions above... Back to you.. Milo

Answer Milos questions and I have one of my own. Any bubbling or gurgling going on when something drains or flushes?
Where's the smell the strongest? Toilet? Drain? Where? Back to you, Tom