NY Fire Sprinkler cheat sheet

Light hazard: design density starts at 0.10 gpm/ft² over 1,500 ft²; Ordinary Group 1: 0.15 gpm/ft² over 1,500 ft²; Ordinary Group 2: 0.20 gpm/ft² over 1,500 ft² (NFPA 13 density/area curves).

Extra hazard Group 1: 0.30 gpm/ft² over 2,500 ft²; Extra hazard Group 2: 0.40 gpm/ft² over 2,500 ft² - densities apply to the hydraulically most demanding area.

Wet pipe systems are the default; dry pipe is limited to spaces subject to freezing, and dry pipe systems require a quicker-opening valve and larger pipe sizing due to water delivery delay.

Pendant sprinklers: deflector 1 in. below noncombustible ceiling; 2 in. to 12 in. below combustible ceiling; sidewall sprinklers have their own spacing and deflector rules.

Maximum coverage per sprinkler: 225 ft² for light hazard (15 ft spacing), 130 ft² for ordinary hazard (15 ft), 100–130 ft² for extra hazard (12 ft).

Sprinkler temperature ratings: ordinary 135–170°F, intermediate 175–225°F, high 250–300°F; color code follows the frame/glass bulb (e.g., red = 155°F, green = 200°F).

Quick-response sprinklers use a Response Time Index (RTI) ≤ 50 (m·s)^0.5; standard-response is RTI ≥ 80; residential sprinklers are listed to NFPA 13R/13D criteria.

K-factor: K = Q / √P, so Q = K√P; a K-5.6 sprinkler at 7 psi flows about 14.8 gpm; K-8.0 at 7 psi flows about 21.2 gpm.

Class I: 2½ in. outlets for fire department use, 100 psi residual at the topmost outlet with 250 gpm for the first riser plus 250 gpm per additional riser up to 1,250 gpm.

Class II: 1½ in. hose stations for occupant use, 100 gpm at 65 psi residual; Class III combines both Class I and Class II outlets.

Automatic wet standpipes require a 2½ in. drain and a pressure-regulating valve where residual pressure exceeds 100 psi at the outlet (175 psi static).

Manual standpipes are permitted only in buildings under construction or where a fire pump is not required; they must be capable of 100 psi at the topmost outlet.

Horizontal standpipe runs and hose connections shall be located so that all portions of the floor are within 30 ft of a nozzle attached to 100 ft of 1½ in. hose (130 ft total travel).

Standpipe risers must be at least 4 in. for Class I/III and 2½ in. for Class II only; pipe sizing is confirmed by hydraulic calculation for combined systems.

Fire department connections: 3 in. for standpipe-only, 4 in. or larger when combined with sprinklers; FDC must be within 100 ft of a hydrant and accessible to apparatus.

NYC Construction Codes reference NFPA 13 (sprinklers), NFPA 14 (standpipes), NFPA 20 (fire pumps), and NFPA 25 (inspection/testing/maintenance) through the NYC Fire Code and Building Code.

NYC Building Code Chapter 9 governs fire protection systems; a construction permit from the NYC Department of Buildings is required before installation or alteration of sprinkler/standpipe systems.

Final acceptance requires a hydrostatic test at 200 psi for 2 hours (or 50 psi above working pressure if higher) witnessed by DOB, plus a successful flow test of the system.

The NYC Fire Code (FC 903, 905) requires annual inspection and testing; sprinkler systems need quarterly and annual checks per NFPA 25 with records maintained on site.

Plan review and sign-off must show hydraulic calculations, water supply (hydrant flow test) data, and the fire pump curve where applicable; NYC requires a licensed master plumber or licensed fire suppression contractor.

New high-rise buildings (75 ft or more) require automatic sprinkler protection throughout and a Class I standpipe with fire pump where residual pressure is insufficient.

NFPA 25 testing intervals: weekly for dry pipe/ deluge valves, monthly for fire pumps (no-flow), annual for main drain and flow switch tests, 5-year internal inspection of piping.

Hydrostatic test: 200 psi for 2 hours for new systems; if working pressure exceeds 150 psi, test at 50 psi above working pressure, minimum 200 psi.

Sprinkler spacing must not exceed the listing; branch line spacing and deflector distance to ceiling must be verified before pressure testing and cover installation.

Main drain test: static and residual pressure readings establish the water supply; a drop of more than 10% between static and residual indicates a partially closed valve or obstruction.

Flushing: underground mains must be flushed at a flow rate sufficient to achieve 10 ft/s velocity before connection to the aboveground system.

Fire pump acceptance test: no-flow (churn), 100% rated flow, 150% rated flow; verify pump curve, suction pressure, and that the relief valve and controller operate correctly.

Inspection records: NFPA 25 requires tagging of sprinkler control valves (open position), monthly gauge readings, and a permanent record of all tests retained for at least one year.

Obstruction investigation is required every 5 years (or when evidence suggests) by flushing the system and examining a representative pipe section for tuberculation or debris.

Final inspection items: correct sprinkler temperature ratings, spare sprinkler cabinet with wrench, unobstructed clearance (18 in. below deflectors), and properly labeled FDC and control valves.