My house is a 1920's downtown house, about 30 feet from the city sewer. Last year we dug out our basement by about 8 inches, so the floor is now 8 inches lower. The floor drain pipes (original iron pipes) crumbled during the dig, so all of the floor drain area was replaced, including a trap. We never had a problem before, but now we have a periodic smell emanating from the floor drain, and when I look inside, there is sewage visible. It is clearly resulting from inside the house, not back-up from the street. We wash it away by dumping buckets of water down the floor drain, and it is gone for another few weeks, but then it eventaully comes back again. We've had the pipes blown out to the street and checked by video, and are quite confident that there's no blockage. The floor drain water level does not rise. Is this a result of having 8 inches less of water pressure on the water in the trap? Is it a result we're going to have to live with, or could the drain plumbing be changed (yet again) to get rid of this annoyance? Thanks in advance for any advice!

we have a periodic smell emanating from the floor drain, and when I look inside, there is sewage visible. It is clearly resulting from inside the house, not back-up from the street. well something's putting backpressure on the drainage otherwise you wouldn't have poop popping up out of your floor drain. Unless you think the "poop fairy" drops around and leaves you a little present from time to time.

Is this a result of having 8 inches less of water pressure on the water in the trap? I don't understand the question. You will only have 2 or so inches of water in your floor drain trap. Where does the 8 inches come from?

Is it a result we're going to have to live with, or could the drain plumbing be changed (yet again) to get rid of this annoyance?
My bet's on the design. You've checked everything else except the layout itself. Can you get your plumber to draw you a diagram of how he did the plumbing? We would like to check it out. Regards, tom