For business and industrial districts, water mains should be at least how many inches?

• A. Six
• B. Eight
• C. Ten
• D. Twelve

Answer: (B)

The main idea here is that districts with higher fire flow demands require larger water mains to supply firefighting operations effectively. The diameter of a water main influences how much water can move and how much pressure is lost as water travels to hydrants and standpipes. In business and industrial areas, the need for greater flow and the possibility of multiple hydrants in use at once mean an eight-inch main provides a reliable balance of capacity and pressure. Six inches is typically seen in residential areas with lower fire demands, while ten or twelve inches are used in especially high-demand or critical feeder situations. So eight inches is the standard minimum to meet the needs of business and industrial districts.