15.4 Fire Protection Systems & Standpipes (NFPA 14)

Fire Protection Systems & Standpipes (NFPA 14)

Content Area H, Fire Protection, is 5 percent of the Florida trade examination. The DBPR reference list tells you precisely which document the questions come from: R66, NFPA 14, Standard for the Installation of Standpipe and Hose Systems, 2019 edition. This section teaches NFPA 14 the way the exam samples it.

A note on scope before the technical material. In Florida, fire sprinkler contracting is licensed separately by the State Fire Marshal under Chapter 633, Florida Statutes, not by DBPR. The plumbing contractor's exam does not ask you to lay out a sprinkler system; it asks whether you understand standpipe classes, sizes, pressures and flows well enough to coordinate with the fire protection contractor and to recognize fire protection piping when you meet it in a shaft.

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1. The Three Classes

NFPA 14 allows a useful substitution: where a building is sprinklered throughout in accordance with NFPA 13 or NFPA 13R, Class II hose stations for use by trained personnel are not required, provided each Class I hose connection is 2-1/2 inch and is equipped with a 2-1/2 by 1-1/2 inch reducer and a cap attached with a chain. That reducer-and-cap arrangement is what you actually see in most modern Florida stair towers.

Wet, Dry, Automatic, Semiautomatic and Manual

The class describes the outlet; these terms describe the water:

• Automatic wet — the standpipe is filled and pressurized, and opening a hose valve delivers the required flow and pressure immediately.
• Automatic dry — filled with pressurized air; a dry-pipe valve admits water when a hose valve opens.
• Semiautomatic dry — filled with air; a remote control device such as a deluge valve admits water when actuated.
• Manual wet — filled with water for detection or priming, but water supply comes only from the fire department pumper through the fire department connection.
• Manual dry — no water at all until the fire department pumps into the FDC. Common in open parking garages.
• Combined system — a riser that supplies both hose connections and automatic sprinklers.

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2. Sizing (NFPA 14 Section 7.6)

[!IMPORTANT] The partially sprinklered case is the trap. Intuition says a partially sprinklered building needs less pipe than an unsprinklered one, so candidates pick 4 inches. NFPA 14 goes the other way: a partially sprinklered combined system must be at least 6 inches, while a fully sprinklered, hydraulically designed combined system may be 4 inches. The 2019 edition revised Section 7.6 specifically to clarify that only partially sprinklered buildings require 6-inch standpipes.

Other arrangement rules:

• Section 7.4: separate standpipes shall be provided in each required exit stairway.
• Section 7.5: where two or more standpipes are installed in the same building or section, they shall be interconnected, unless the AHJ accepts otherwise. Where supplied by tanks at the top of the building or zone, they are interconnected at the top; where wet standpipes are interconnected at top and bottom, check valves shall be installed at the base of each standpipe to prevent circulation; dry standpipes shall have only a single level of interconnection.

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3. Pressure (NFPA 14 Section 7.8)

Section 7.8.1, Minimum Design Pressure for Hydraulically Designed Systems, is the sentence to memorize:

Hydraulically designed standpipe systems shall be designed to provide the waterflow rate required by Section 7.10 at a minimum residual pressure of 100 psi (6.9 bar) at the hydraulically most remote 2-1/2 inch (65 mm) hose connection and 65 psi (4.5 bar) at the outlet of the hydraulically most remote 1-1/2 inch (40 mm) hose connection.

The 100 psi figure is not arbitrary: combination nozzles on fire department attack handlines are designed to operate at 100 psi at the nozzle, so the standpipe must deliver it at the outlet.

Maximum pressure: where the residual pressure at a hose connection exceeds 175 psi (12.1 bar), a listed pressure-regulating device shall be provided to limit the pressure at that connection to not more than 175 psi. In a tall building the standpipe is divided into pressure zones for exactly this reason: at 0.433 psi per foot of elevation, a single zone more than roughly 400 feet tall cannot keep the bottom outlets under 175 psi while keeping the top outlets at 100 psi.

Manual standpipe systems are designed under Section 7.8.1.2 to provide the required flow and pressure with the demand supplied at the fire department connection, so the FDC pressure requirement is calculated back from the most remote outlet.

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4. Flow (NFPA 14 Section 7.10)

For Class I and Class III systems:

• Minimum flow for the hydraulically most remote standpipe: 500 gpm, delivered through the two most remote 2-1/2 inch outlets.
• Each additional standpipe: 250 gpm.
• For buildings exceeding 80,000 square feet per floor, the second standpipe is calculated at 500 gpm and the third at 250 gpm.
• Maximum flow rate: 1,000 gpm where the building is sprinklered in accordance with NFPA 13, and 1,250 gpm where it is not.
• Class II systems require 100 gpm.

Worked example. A six-story, unsprinklered Florida office building has three exit stairways, each with a Class I standpipe, and 45,000 square feet per floor.

1. Each required exit stairway gets its own standpipe under Section 7.4: three standpipes.
2. The hydraulically most remote standpipe carries 500 gpm.
3. The floor area is under 80,000 square feet, so the two additional standpipes carry 250 gpm each = 500 gpm.
4. Total system demand = 500 + 250 + 250 = 1,000 gpm.
5. Check the ceiling: the building is not sprinklered to NFPA 13, so the maximum is 1,250 gpm. The 1,000 gpm demand is within it.
6. The supply must deliver that 1,000 gpm at a residual pressure of 100 psi at the hydraulically most remote 2-1/2 inch hose connection, which on the sixth floor of the most remote stair also means overcoming roughly 0.433 psi per foot of elevation plus the friction in the riser and branch lines.

Had the same building been sprinklered throughout to NFPA 13, the 1,000 gpm cap would apply — and the standpipe could be 4 inches under Section 7.6.3 rather than 6 inches under 7.6.2 if it were only partially sprinklered.

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5. Hose Connection Locations (NFPA 14 Section 7.3)

Class I hose connections are required at the main floor landings of exit stairways, on each side of the wall adjacent to the exit opening of a horizontal exit, and at additional locations the standard specifies. Beyond those:

• 7.3.2.6: hose connections in covered mall buildings at the entrance to each exit passageway or exit corridor and at the interior side of public entrances from the exterior to the mall.
• 7.3.2.7: a hose connection at the highest landing of stairways with stairway access to a roof; 7.3.2.9 requires a roof connection in stairways that do not access the roof, not required where the roof slope is 4 in 12 or greater or where a 7.3.2.7 connection exists.
• 7.3.2.10: additional hose connections in unsprinklered buildings where the distance from the required connections to the most remote portion or story exceeds 150 feet (45.7 m).
• 7.3.2.11: additional hose connections in buildings sprinklered to NFPA 13 or NFPA 13R where that distance exceeds 200 feet (61 m). The distance is measured from the hose connection, does not apply to a roof not intended for occupancy, and additional connections may be omitted where allowed by the AHJ.
• 7.3.2.12: in open parking garages, those distances are reduced to 130 feet (39.7 m) where manual dry standpipes are installed.
• 7.3.3.1: Class II travel distance limits apply to Class II systems; 7.3.4.1.1 states that the travel distance limitation does not apply to Class III systems.
• 7.3.2.5: hose connections shall not be spaced greater than 75 feet apart in the circumstance that section addresses.

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6. Where the Plumbing Trade Meets Fire Protection

Four intersections come up on Florida jobs:

1. The fire service main and the domestic service. They often share a trench and a tap. The fire line's backflow protection is typically a double check detector assembly (ASSE 1048) or, for a hazard, a reduced pressure detector assembly (ASSE 1047) — both named in FPC Sections 608.14.2 and 608.14.7.
2. The fire department connection (FDC). Sized and located with the fire protection contractor, but the plumbing contractor is often the trade that coordinates the wall penetration, the sleeve and the drainage away from it.
3. Standpipe drains and test connections. Main drains and inspector's test connections discharge where they will not damage the building and, where they reach the drainage system, do so as indirect waste under FPC Chapter 8.
4. Residential sprinklers. Florida's residential code permits dwelling-unit sprinkler systems designed to NFPA 13D and, in multifamily, NFPA 13R. Where such a system is supplied from the domestic water piping, the cross-connection and material questions are plumbing-code questions.

[!NOTE] Reclaimed water and fire protection do not mix by default. Section 6.3 of this guide lists fire sprinkler systems among the strictly limited uses for reclaimed water, permitted only where approved by the State Fire Marshal. Do not connect a reclaimed main to a fire service without that approval in hand.