Our basement has water backing up from the sewage line every time we do laundry. We had a plumber clean out the line 3 months ago. They went through the house and not the larger outdoor opening. I had someone out today who cleaned out through the outdoor opening. There was a lot of root growth. We did 3 loads of laundry tonight and the basement is flooded with sewage backup. I don't know what else we can do. Any suggestions?