Sewers are classified as follows:
COMBINED SANITARY AND STORM SEWER. A sewer which is not designated as either a storm sewer or sanitary sewer is designed for this use.
MAIN SEWER. One designed to carry the entire sewage or water of a municipality or sewerage district to the sewer outlet, septic, or disposal plant.
SANITARY SEWER. One designed solely to carry sewage and wastes from buildings or structures. The term SANITARY SEWER shall exclude drainage from roofs, sidewalks, roadways, streets, alleys, or other surface drainage.
SERVICE SEWER. One designed to carry sewage or water from the property abutting upon the street or way in which it is laid into a trunk or main sewer, or into the sewer outlet, septic, or disposal plant.
STORM SEWER. One designed solely to carry storm or surface waters.
TRUNK SEWER. One designed to carry the sewage or water from any particular district or portion of the municipality as well as the sewage or water from property abutting upon the street or way in which it is laid, and of sufficient capacity to carry the sewage or water from the service sewers in the district or portion of the municipality in which it is laid, to the main sewer outlet, septic, or disposal plant.
(SDCL § 9-48-1)