Long story short. There is a drain in the basement mostly for the ac and the hot water heater. I assume the kitchen sink connects up to this drain as well. Once time when the garbage disposal was over worked during canning season, the drain backed up into the basement and we had a mess.

Anyway, Last year we called out a plumber to fix the drain it was very slow. He cleared it up and we haven't had any problems until the city came by and "cleaned" out their pipes. Now we have a bad sewer gas smell coming back into the basement. It's not bad most of the time, but the past couple of days we've had to keep the door closed and won't go down there for very long. I do pour water down the drain thinking the trap went dry. I called the city and told them this problem started after their cleaning. They came to check it out but claim it's not their fault. The floor is dry meaning the water we use isn't backing up into the basement.

So do I need to call a plumber, or do is there something I can do myself to stop this foul smell?