replying to SoloMan, soloman wrote: Now that I am thinking about it, for the past few months, occasionally there would be a smell in the downstairs level of my home. I tended to think that it came from the bathroom and/or shower drain. The same drain that backed up last week.
There is a P trap in there and I would run the water weekly just to make sure it was filled. But perhaps the plumbing was "slightly" backing up causing there to be a slight mixture of sewage water in the P trap of that shower? It definitely never came up through the drain before, but there was definitely a smell. I remember pouring some bleech down that drain a few months ago because of the smell. And I remember smelling a smell Wednesday night, the night before the sewage started backing up through the drain.
Perhaps this issue was coming for awhile now and finally reached the point of no return last week.