Components of Basic Wet-Pipe Riser Assemblies

This week we're covering a basic riser manifold configuration for wet-pipe fire sprinkler systems. This is not for a shotgun-style single riser, nor for a wet riser using an alarm check valve (we'll explore both of those later).

​If you haven't checked it out, there are great ongoing discussions (some of which covered these topics) on the MeyerFire Daily page here. 

Overview
Wet-pipe systems form the backbone of traditional fire sprinkler system design, comprising the most popular and most economical system type available. Here's the major components that go into a wet-pipe fire sprinkler assembly:

Check Valve

• Purpose: Allows the system to retain pressure over time, prevents and siphonage of water in a system to serve standpipes or other systems, and helps prevent nuisance waterflow alarm paddle movement by maintaining water in each system.
• Where Required: a check valve is required in any system, but may also be accomplished by a single backflow preventer in a multi-system manifold. Check valves are required on each sprinkler system where the supply serves both sprinklers and standpipes.
• Orientation: must be horizontal or vertical-up in accordance with its listing (NFPA 13 2002 8.15.1.1.3.4, 2007 -16 8.16.1.1.3.4, 2019 16.9.5.4)

FDC Connection

• Purpose: Allows the fire department to supply supplementary pressure and flow to the system during a fire event.
• Where Required: on any sprinkler system that does not meet exceptions for being inaccessible, large-capacity deluge systems, or single-story buildings not over 2,000 sqft (185 sq.m.). (NFPA 13 2002 8.16.2.2, 2007-16 8.17.2.2, 2019 16.12.2)
• Where Located: for a single system it must be on the system side of the main system control valve, check, and alarm valves, and is permitted to be connected to the main piping directly (NFPA 13 2002 8.16.2.4.2, 2007-16 8.17.2.4.2, 2019 16.12.5.2), for multiple systems the FDC connection must be between the supply control valves and system control valves (on the manifold) (NFPA 13 2002 8.16.2.4.3, 2007-16 8.17.2.4.3, 2019 16.12.5.4).

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Main Drain

• Purpose: Allows the system to be drained down for maintenance, interior inspections, repair, or modifications.
• Discharge: must discharge to outside or to a drain connection, but not directly to a sewer (NFPA 13 2002 8.15.2.6.1, 2007-16 8.16.2.6.1, 2019 16.10.6.1)
• Labeled: required to be labeled with a weatherproof metal or rigid plastic identifier (NFPA 13 2002-16 6.7.4.1, 2019 16.9.12.1)
• Size: is determined by NFPA 13 (2002 Table 8.15.2.4.2 and 8.15.2.6, 2007-16 8.16.2.4.2, 2019 16.10.4.2)

Inspector's Test

• Purpose: Allows the waterflow switch to be tested as required by NFPA 25 by flowing water, and allows drainage of the system.
• Where Required: for wet systems, anywhere downstream of the waterflow alarm. Some jurisdictions have requirements or preferences to locate the inspector's test remotely from the riser (NFPA 13 2007-13 8.17.4.2.4, 2016 8.17.4.1.4). Note that FM Global systems require wet system inspector's tests to be located remotely from the riser (FM Global 2-0 2.6.5)
• Approved: required to be approved (NFPA 13 2002-13 6.7.3, 2016 6.6.3, 2019 16.9.1.1).
• Labeled: required to be labeled with a weatherproof metal or rigid plastic identifier (NFPA 13 2002-13 6.7.4, 2016 6.6.4, 2019 16.9.12).
• Orifice: The orifice (within a sight/site glass) simulates the flow of a single sprinkler in order to ensure that the sprinkler waterflow alarm will activate upon the flow of a single sprinkler. The orifice must: be equal to the smallest orifice of any sprinkler installed on the system (NFPA 13 2002 8.16.4.1.1, 2007-16 8.17.4.1.1, 2019 16.14.1.1), and be smooth bore and corrosion resistant (NFPA 13 2002-13 8.17.4.2.1, 2016 8.17.4.1.1, 2019 16.14.1.1)
• Sight/Site Glass: typically provided where water discharge is not visible from the control valve (NFPA 13 2002 A.8.16.4.2, 2007-13 A.8.17.4.2, 2016 A.8.17.4.1, 2019 A.16.14.1). 

Isolation Valve

• Purpose: Allow a single system to be shut off for maintenance, inspection or renovation. Limiting the system size per isolation valve also helps reduce risk that a large facility wouldn't be affected by the closure of a single system valve.
• Where Required: isolation valve is required on each sprinkler system (NFPA 13 2002 8.15.1.1.1, 2007-16 8.16.1.1.1.1, 2019 16.9.3.1.1)
• Accessible: valve is required to be readily accessible for operation, inspection, tests & maintenance and located where free of obstruction (NFPA 13 2002 8.16.4.2.2, 2007-2013 8.17.4.2.2, 2016 8.17.4.1.2, 2019 16.14.1.2, FM Global 2-0 2.6.5). Are recommended to be no more than 7 feet above finished floor (NFPA 13 2002 A.8.16.4.2, 2007-13 A.8.17.4.2, 2016 A.8.17.4.1, 2019 A.16.14.1)
• Identification: must include portion of building served and what it controls (NFPA 13 2002-13 6.7.4.3, 2016 6.6.4.3, 16.9.12.3), and it's function (NFPA 13 2002 8.15.1.1.8, 2007-16 8.16.1.1.8, 2019 16.9.3.5)
• Indicating: must show it's position and be visible when standing at floor level (NFPA 13 2002 8.15.1.1.2.4, 2007-16 8.16.1.1.2.4, 2019 16.9.3.3.4)
• Listed: this valve is required to be listed (NFPA 13 2002-13 6.7.1.3, 2016 6.6.1.3, 2019 16.9.3.2)
• Supervision: can be accomplished by (1) central, proprietary or remote station, (2) a local sounding at a constantly attended location, (3) locked in correct position, (4) within fenced inclusion under control of owner, sealed, and inspected weekly (NFPA 13 2002 8.15.1.1.2.1, 2007-16 8.16.1.1.2.1, 2019 16.9.3.3.1)

Pressure Gauge

• Purpose: To assess loss of pressure over time during testing and to verify the water pressure in a system.
• Where Required: above and below each alarm check valve or system riser check (when present) (NFPA 2002 7.1.1.2), and adjacent to main drain (NFPA 13 2002 8.16.3.1, 2007-16 8.17.3.1, 2019 16.13.1)
• Accessible: must be accessible for operation, inspection, tests & maintenance (NFPA 13 2002-16 8.1.2, 2019 16.1.1)
• Capacity: The maximum limit for the gauge must not be less than twice the normal working pressure at the point in the system where it's installed (NFPA 13 2002 8.16.3.3, 2007-16 8.17.3.3, 2019 16.13.3)
• Connection: must be minimum 1/4-inch thread inlet near main drain (NFPA 13 2002 8.16.3.1, 2007-16 8.17.3.1, 2019 16.13.1)
• Listed: required to be listed (NFPA 13 2002 8.16.3.3, 2007-16 8.17.3.3, 2019 16.13.3)
• Removal: must permit removal and not be subject to freezing (NFPA 13 2002 8.16.3.4, 2007-16 8.17.3.4, 2019 16.13.4)

Waterflow Switch

• Purpose: To transmit an alarm signal to the fire alarm system and/or supervising station that the sprinkler system is active.
• Where Required: Is required for each zoned system. (NFPA 2002-13 6.9.2.1, 2016 6.8.2.1, 2019 16.11.3.1)
• Listed: required to be listed (NFPA 2002-13 6.9.2.1, 2016 6.8.2.1, 2019 16.11.3.1)
• Supervision: must be supervised (NFPA 2002-13 6.9.2.1, 2016 6.8.2.1, 2019 16.11.3.1)

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