Sewer gas

[Ed from chicago]

Hi guys,

My wife claims that when she washes dishes recently, that she can smell sewer gas in the basement. We live in the mdwest and have a catch basin. There is a bar sink, and laundry tub connected to the same sewer line, and there is also a floor drain in the basement next to the tub. What can be causing the gas to backup?

Thanks very much.

P.S. I have no sense of smell, so it's hard for me to figure out where it's coming from.

[statjunk]

My uneducated guess is that something isn't properly vented and the trap is being sucked dry.

Tom