California Code, Public Utilities Code - PUC § 230.5

“Sewer system” includes all real estate, fixtures, and personal property owned, controlled, operated, or managed in connection with or to facilitate sewage collection, treatment, or disposition for sanitary or drainage purposes, including any and all lateral and connecting sewers, interceptors, trunk and outfall lines and sanitary sewage treatment or disposal plants or works, and any and all drains, conduits, and outlets for surface or storm waters, and any and all other works, property or structures necessary or convenient for the collection or disposal of sewage, industrial waste, or surface or storm waters.  “Sewer system” shall not include a sewer system which merely collects sewage on the property of a single owner.