My problem started with water/sewage backing up in shower and coming out of bottom of toilet. The shower, sink, and toilet are all side by side and use the same drain pipe to the septic tank. I took the toilet off and had a plumber come to snake, scope, and clean the line. They discovered the drain, which goes to the left of shower was clean and instead found that the the toilet's vent pipe which goes to the right had broken underground and closed off. The toilet sits in front of the bathroom window and on the other side of the window the vent pipe comes out of the ground. The plumber says that to replace the vent pipe will cost $4000, which seems high to me. Can anyone suggest alternatives/questions I could ask the plumber? Thanks.