For business and industrial areas, hydrant supply mains minimum size?

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

Answer: (B)

Sizing hydrant supply mains is about maintaining adequate flow and pressure for hydrants during a fire. In business and industrial districts, the demand on the water supply is higher because fires can involve larger buildings, more equipment, and multiple hydrants may be used at once. That’s why the minimum main size is eight inches: it reduces friction losses and helps keep the residual pressure at hydrants when high flows are needed. A smaller main, like six inches, can’t reliably support those simultaneous high demands without dropping pressure too much. Larger sizes, such as ten or twelve inches, are used only in larger districts or special systems, but eight inches is the standard minimum for these areas.