A large sewer serving two or more sewer mains is called a trunk main.

• A. Branch main
• B. Trunk main
• C. Collector
• D. Interceptor

Answer: (B)

In a sewer network, large conduits gather flow from multiple smaller lines to move it toward treatment facilities. A trunk main is exactly that: a large-diameter pipeline that collects sewage from two or more branch mains and carries it onward toward interceptors or a treatment plant. This contrasts with a branch main, which is smaller and feeds into a larger trunk; a collector, which gathers wastewater within a district toward a trunk or interceptor; and an interceptor, which carries sewage from collection systems to treatment facilities, often over longer distances. So the description fits a trunk main because it describes a large line that serves several mains and consolidates their flow.