All of the drains in your home have to lead somewhere. And unless you have a septic tank on your property, the sewer line leads out to the sewer main that services the city. The sewer main is at the end of your property, under the street in most cases.
What many homeowners don’t realize is that they are responsible for any damage suffered by the sewer line, all the way up to the sewer main. You cannot count on someone else to take care of this for you. If you have problems with the sewer lateral, get the right plumber for the job.