I have a sewer smell coming from just a section of pipe in my basement. It's not pvc piping. The pipe leads up to the second floor bathroom. I've tried baking soda with vinegar and bleach. I noticed the bleach smell directly after pouring it down the drains in the second floor bathroom. The shower doesn't get used so I ran the water for a while, but that didn't work. I'm definately confused as to what I can do next before calling a plumber. Could it be that gas is getting out from where the pipes join? Would patching these help (and what would I use)?

thank you for your help