Occasional sewer back-up
#1
I'm having a problem with the main sewer backing up on occasion. Have had a plumber clean out the drain several times, but the problem persists. Dosen't seem to be any kind of pattern cause. It seems like the line is clogged somewhere outside, as the water will not back up until after everyone has showered and bathed or we have run a lot of laundry. Plumber says that he has gone all the way out to the city line and can't find any blockage. HELP!!!! This is driving me crazy.