What it means
A gravity sewer depends on pipe slope, pipe condition, adequate flow, and clear pathways. If slope is too flat, solids can settle. If pipes are damaged or blocked, wastewater can back up or overflow.
What operators watch
- Slope, velocity, and pipe condition affect solids transport.
- Manholes provide access for inspection, cleaning, and maintenance.
- Roots, grease, rags, sediment, and structural defects are common problems.
Common exam traps
- Thinking gravity systems need no operational attention.
- Ignoring minimum velocity and solids deposition.
- Confusing collection sewers with storm drains.
Field example
A recurring blockage in a flat section may require cleaning frequency changes, CCTV inspection, or repair planning.
