In business and industrial districts, hydrant supply mains should be at least how many inches?

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

Answer: (B)

The main idea is that hydrant supply mains in business and industrial districts must have enough capacity to deliver the fire flow needed without excessive pressure loss. In these areas, the potential for higher fire loads, larger streams, and multiple hydrants operating at once means the water mains should be sized to keep pressures usable while meeting demand. Eight inches is the standard minimum because it provides ample capacity to support typical industrial and commercial fire flows and simultaneous hydrant use, while keeping costs reasonable. A six-inch main is usually seen in residential or smaller commercial areas with lower fire flow demands, and larger sizes like ten or twelve inches are chosen only for very high-demand situations or major feeders, not as the general minimum for these districts.