Which type of distribution system piping generally runs straight lines and has few side connections?

• A. Service lines
• B. Distribution mains
• C. Transmission mains
• D. Local mains

Answer: (B)

In a distribution system, the main lines that act as the backbone for feeding large areas are designed to carry water efficiently with minimal branching. These distribution mains typically run in relatively straight alignments to move water across neighborhoods and commercial districts with fewer taps, making pressure and flow easier to control and maintain. They connect to smaller feeders and service lines at designated points, but the length of straight, uninterrupted run is a defining feature of this backbone.

Service lines are the tap-offs to individual customers, so they’re short and highly branched. Local mains branch off from the backbone to serve specific streets and areas, thus they have more side connections. Transmission mains, while large and long-distance, are primarily about moving water from treatment facilities to the distribution network and are not the everyday distribution backbone within a service area.