Need some help. Got an upstairs bathroom where the toilet and tub are separated with a door. Early in the morning that area reeks of raw sewage. In the evening all is well. This has been going on for weeks and has happened on and off for the past two years. I thought it was a dead animal in the attic, but if it was, why does the odor go away in the evening? The tub does not get used much, and neither does that toilet. Do I have a plumber check it out, or someone else. I cannot figure it out. Thanks!