I have a front loading washing machine located on the second floor in a bathroom. There seems to be a sewer smell that randomly occurs which seems to come from it or the area around it. I actually stuck my head inside the machine and the smell is horrible and NOT mold. There is also a safety drain in the floor that is connected to the drain for the washer. It has a trap, and I recently blocked it off because my thinking is that if water isn't running through it daily it will evaporate from the trap and not block the gases. This is the first test to see if it continues.
The thing that doesn't make sense is that the inside of the washer stinks like sewer gas, but doesn't smell where the flexible drain pipe connects to the PVC drain in the wall. And, yes, there is a trap on that drain. Anyone experience anything like this?