I had a clog recently at the cleanout that is about 15 feet before the town sewer line. A plumber cleared it out but advises me to have the
entire 15 feet replaced "because something isn't right with it".
When I look down the cleanout about 10 feet below ground I can see standing liquid and if someone were to flush the toilet I would see liquid rush by and then there would be the standing liquid afterwards. Does anyone know if it's normal to see standing liquid like this?
All drain liquid should flow right on through the line unless it has an obstruction (roots?), a break (dirt? roots?), or a dip in the line due to compaction or settling.
Sounds like it needs to be inspected with a video camera to see exactly what you're dealing with, or just go ahead and dig it up and replace it with a new line with the proper slope.