According to NFPA 20, what is the minimum number of water tanks required as the primary source in a very tall building?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (B)

The situation tests redundancy and sufficient water supply for fire pumps in very tall buildings. NFPA 20 requires more than one primary water source to ensure the pump has a reliable, adequate supply and pressure, even if one source is unavailable or compromised. In very tall structures, a single water tank may not provide the needed head or volume to feed the fire pump across all floors, so using two primary tanks—often arranged to supply in parallel or at different elevations—gives a backup and preserves suction, preventing loss of pressure during a fire event. While additional tanks could be used for extra capacity, the minimum required for a primary source in a very tall building is two.