The homeowner is usually responsible for the sewer line that runs from the house to the connection at the city main, a pipe called the lateral. The municipality owns and maintains the sewer main in the street. The exact dividing point varies by city, so homeowners should confirm it locally.
The pipe you own is the lateral. It carries wastewater from your home’s plumbing out under the yard to the point where it joins the public system. In many places that responsibility covers the entire lateral, including the section buried under the sidewalk or street, right up to the connection at the main. Los Angeles County Public Works, for example, states that the property owner is responsible for the entire length of the lateral, including the portion within the public right of way.
The city or a sanitary district owns the sewer main, the larger pipe running down the street that collects flow from every lateral on the block. Where your responsibility ends and the city’s begins is the part that changes from place to place. Some cities draw the line at the main itself. Others stop homeowner responsibility at the edge of the public right of way or the property line and maintain the connection beyond it. Because of this, a repair that is yours in one city could belong to the utility a few miles away.
If you live in the Dallas-Fort Worth area, confirm the exact dividing line with your city’s water or public works department before you assume a backup is yours to fix. When the problem sits on your side, a camera inspection shows where the damage is, and trenchless methods such as pipe lining can often repair that section without digging up the yard or the street.