My drain in my laundy room and drain by the hot waterheater are over flowing. It seems to only happen after you shower or drain the bath tub. The toilet will gurgle then it will over flow. I should tell you we share a main line with the townhouse next to us. Also the toilet pipes join together. If we flood so does next door and vice versa. The plumber came and snaked it and said it was toilet paper but this has happened 3 time in one week. And they have snaked it 2 times. Sludge black is coming out.

Get the plumber to run a camera through the pipes to determine what the problem might be. Let us know the results, tom