How deep a sewer line is buried usually ranges from about 12 inches to several feet, driven mostly by your region and the local frost line. In warm climates like Texas, the line can sit fairly shallow. In colder regions it runs below the frost line, which may reach several feet deep.
Across the country, residential sewer lines commonly fall between about 18 inches and 6 feet below grade, and regional averages track the climate. In the South, including North Texas, lines often run roughly 2 to 5 feet deep, while the Midwest and Northeast reach 4 to 8 feet because the ground freezes deeper there. The pipe also does not stay at one depth: it slopes toward the city main, starting shallow near the house and dropping as it runs, so the street connection can sit much deeper than where the pipe leaves your foundation.
In colder regions, local plumbing code sets a minimum depth tied to the frost line, the level at which soil freezes each year, so water in the pipe cannot freeze and crack it. The colder the climate, the deeper that line generally runs. Texas has a shallow frost line, so depth here is set more by slope and surface protection than by freezing.
The only way to know how deep your specific line sits is to locate it, because published ranges are averages, not your yard. A sewer camera fed through a cleanout can be traced from the surface to read the pipe’s depth and path; this is what a camera inspection does. That detail matters before any work, since a deeper line is harder and costlier to reach by open digging, which is one reason many homeowners choose a trenchless pipe repair.