Sanitary Sewer: Definition & Professional Guide
Call Now (855) 557-9600
A sanitary sewer is an underground pipe system designed to transport wastewater and sewage from residential, commercial, and industrial buildings to a municipal wastewater treatment plant for processing and safe discharge. Unlike storm sewers that carry rainwater, sanitary sewers carry only domestic and commercial wastewater — toilet waste, sink drainage, laundry water, and other used water from building plumbing systems.
Gravity Slope, Lateral Ownership Boundary & Lift Station Operation
The sanitary sewer system operates primarily by gravity, with pipes laid at a consistent downward slope from individual building connections to progressively larger collector mains, trunk sewers, and interceptors that converge on the treatment plant. The typical slope for residential sewer laterals is one-quarter inch per foot for 4-inch pipes and one-eighth inch per foot for larger mains. This pitch generates enough velocity (2 to 10 feet per second) to transport both liquids and solids without allowing material to settle and create blockages.
Each building connects to the sanitary sewer through a building sewer lateral — a pipe that runs from the building drain at the foundation to the municipal sewer main, typically located under the street or in a utility easement. The connection point at the main is called the sewer tap. The property owner is responsible for maintaining the lateral from the building to the tap, while the municipality maintains the main and all downstream infrastructure.
In areas where terrain makes gravity flow impossible, lift stations (pump stations) raise wastewater from low-lying collection areas to higher-elevation mains, where gravity flow can resume. Municipalities in flat, high-water-table regions operate numerous lift stations throughout their sewer service areas due to topographic constraints.
Gravity, Pressure Force Main, Low-Pressure & Vacuum Sewer Types
Gravity sanitary sewers are the most common type, using the slope of the pipe to move wastewater without mechanical assistance. Pipe diameters range from 4 inches for building laterals to 48 inches or larger for interceptor mains.
Pressure (force main) sanitary sewers use pumps to move wastewater through pressurized pipes where gravity flow is not possible. These connect lift stations to gravity mains at higher elevations.
Low-pressure sewer systems use individual grinder pumps at each property to pressurize wastewater through small-diameter (2 to 4 inch) collection mains. These are used in areas where conventional gravity sewer installation is impractical due to flat terrain, high water tables, or rocky subsurface conditions.
Vacuum sanitary sewers use a central vacuum station to pull wastewater through sealed pipes using negative pressure. These are uncommon but used in some coastal communities where high water tables prevent gravity sewer installation.
Sewer Lateral Repair, Camera Inspection & Backwater Valve Services
Bonded Plumbworks’ drain and sewer services address the building-side connection to the sanitary sewer system. Services include building sewer lateral repair and replacement, sewer line inspection using camera and video pipe inspection, root removal, trenchless sewer repair, and cleanout installation.
When a sanitary sewer main backs up into a building through the lateral connection, a backwater valve prevents sewage from reaching interior fixtures. Bonded Plumbworks installs backwater valves as a proactive protection measure for homes in areas with a history of sewer surcharges.
State Building Code, ASTM D3034, C76 & DEP Discharge Permits
The applicable state building codes governs building sewer lateral installation, including pipe material, slope, depth, and connection methods. The state department of environmental protection regulates municipal sanitary sewer systems and treatment plant discharge permits. ASTM D3034 governs PVC sewer pipe. ASTM C76 covers reinforced concrete sewer pipe for larger mains.
Charlotte Pipe, Advanced Drainage Systems, Contech & Fernco Products
Charlotte Pipe produces PVC sewer pipe and fittings for building laterals. Advanced Drainage Systems (ADS) manufactures corrugated HDPE sewer pipe. Contech produces reinforced concrete pipe for municipal mains. Fernco provides flexible couplings for sewer pipe connections and repairs.