What is wrong when sand is being pulled out of the main track of a plumbing line?
This is a good indication that you have a hole in your sewer
line. It could be from root intrusion via a bad joint. It could be
a bad joint. Perhaps a collapsed line due to the pipe material
itself. Some older homes used a sewer material called orangeberg
which was discontinued because it was structural unstable and prone
to all sorts of problems.