We have a bad smell behind our washer. After much research, I am beginning to think that it is coming from the washer drain pipe. Is it possible that it is sewer gas coming back up through the pipe? Do washer drain pipes have traps? We live on a slab. We have the wall ripped out behind the washer and can follow the washer drain pipe the entire way to the floor and there is not a trap visible. Any suggestions. It is very stinky and embarressing. Any help or suggestions would be greatly appreciated.

Thanks!!

How old is your house? Was the washer drain added afterwards? Any drainge problems connected to the washer?
I'm going to post up a very poor freehand drawing of a washer set up. This drawing my look like your five year ould childdrewt but it's accurate.
If, after you've opened up the wall, you don't find a second pipe that serves as the vent chances that you're correct and you're not trapped and the floor should come up and the washer trapped and vented. Good Luck, Tom