What is the minimum water supply requirement for Class I, Class II, and Class III systems?

• A. The minimum water supply shall be capable of providing the system demand established by Sections 7.8 and 7.10 for at least 30 minutes
• B. 30 seconds
• C. 60 minutes
• D. Indefinite supply

Answer: (A)

Standpipe systems are designed to provide a sustained water supply for firefighting and occupant use, and the minimum requirement is that this supply can meet the system’s calculated demand for a set period. For Class I, II, and III standpipes, that period is at least 30 minutes. The system demand is determined by the hydraulically calculated requirements in Sections 7.8 and 7.10, which account for things like pipe length, fittings, elevation, and any pumping or storage needed. This 30-minute duration ensures there is enough water to initiate and sustain an attack at the standpipe outlets without an immediate loss of pressure or flow, giving firefighters time to connect, deploy, and use the system effectively. The other options don’t fit because 30 seconds is far too short for a sustained attack, 60 minutes exceeds the minimum requirement, and indefinite supply isn’t mandated by NFPA 14 for typical standpipe systems.