Sanitary Sewer
CSI Division 33, Utilities
The underground gravity or pressure piping that carries a building's wastewater from its connection point to the municipal sewer system (or a septic system where no municipal sewer is available), sized and sloped to the local plumbing code's exact requirements for gravity flow.
Why it matters
A sanitary sewer line that isn't sloped correctly won't fully self-clean during normal flow, letting solids settle and eventually clog the line, a problem that's completely invisible from the surface and often isn't discovered until a backup happens well after the site is paved over.
On a real project
A site's sanitary sewer line is installed at the minimum slope the plumbing code requires for its pipe size, verified with a laser level during installation and confirmed again with a video inspection before backfill covers the pipe for good.
Who this matters most to
A Plumber or utility contractor installs and tests the underground sanitary sewer connection between the building and the municipal main. An Equipment Operator excavates and backfills the sewer trench to the depth and bedding the plumbing code and manufacturer both require.
Where this goes wrong
A sanitary sewer line is installed slightly flatter than the code-required minimum slope to avoid a deeper, more expensive excavation, and the discrepancy isn't caught before backfill. Within the building's first year of occupancy, solids settle in the under-sloped section and cause a backup that requires excavating back into the finished site to locate and correct.