A bunch of folks have talked about roots in their sewer (as evidenced by water coming back up their basement, sinks, … whatever — or as determined by roto-rooter or camera services; each case is a bit different). Below are a few pics of what it means to have roots in the line.

In this first image, note the root centered in the pic that is about as wide as the 3″ pipe (that pipe isn’t sewer):

This next image is of a 2-3′ length of 6″ terracotta (what had been the lateral), with the black rootmass that was the blockage having fallen out. (There was more length of each, not pictured here; there was about 4-5′ of rootmass inside the pipe in total):

The following shows the city crew installing a new lateral and cleanout/tap — I post this to illustrate that the main line is only about 6 feet below street level (I’ve heard some story about a contractor providing a pricey estimate explaining that the main is likely 15-20′ below ground. That may be the case somewhere, but was not the case where this work was conducted.):

BTW — the city crew was said to be awesome.