Standpipe Systems
Standpipe Systems covers Class I/II/III systems, flow and pressure, valve locations, and combined sprinkler/standpipe design under NFPA 14 and NYC BC 905. The exam tests whether you can select the right class and prove the top outlet works.
Classes
Class I: 2.5-in. hose valves for fire department use. Class II: 1.5-in. valves for occupant use, limited in NYC. Class III: both. Outlet height is typically 3–5 ft above floor, and valves must be accessible.
Hydraulics
NFPA 14 minimum residual pressure at the topmost outlet is 100 psi for 2.5-in. outlets and 65 psi for 1.5-in. outlets. Typical design flows are 500 gpm for Class I, 250 gpm for Class II, and 500 gpm for Class III. The supply must also overcome elevation (0.433 psi/ft) and friction.
Worked example
Top outlet 120 ft above the pump, 100 psi required, friction 15 psi. Elevation = 120 × 0.433 = 52 psi. Base pressure = 100 + 52 + 15 = 167 psi, before any PRV. If the city supply cannot hold that, a fire pump or tank is needed.
Traps
Confusing residual pressure at the top outlet with pump discharge; ignoring PRVs; treating manual and automatic standpipes as equivalent; missing horizontal standpipe coverage; using 65 psi for a 2.5-in. outlet.