Technical Justification for Large Diameter Fire Department Connections
Authorities Having Jurisdiction (AHJ) around the county have started requiring the installation of thread-less quick connect, large diameter style fire department connections (FDC) in new construction. This use is largely based on the assumption that the larger diameter is probably capable of providing the required flow, but their use should trigger us to ask several questions about their actual capabilities. The first being, are they allowed by the standards that govern their use? Secondly, do they meet or exceed the current requirements for flow? The traditional 2 ½ inch inlets have also been used for many years with no substantiation for their use regarding specific flow capabilities. This all changed in 2007, when the NFPA 14 Technical Committee added the requirement for 2 ½ inch inlets to be sized to provide 250 gallons per minute. That requirement for flow sizing, triggered the Fire Protection Research Foundation (FPRF) to convene a full-scale flow test research study to provide data to support the 250 gallon per minute requirement. In 2015, the NFPA Research Foundation publicized their findings for 2 ½ inch inlets, in the Fire Department Connection (FDC) Inlet Flow Assessment. This study gives the technical justification to the validity of the 250 gallons per minute requirement of the traditional 2 ½ in inlets. This study only addressed 2 ½ inch FDC’s and did not address the use of any large diameter quick connect FDC’s.
As we start to look at the use of the large diameter FDC’s, let us begin with what an FDC is and what it is required to provide in terms of flow. NFPA 24-2019 Standard for the Installation of Private Fire Service Mains and Their Appurtenances, gives a definition for a fire department connection. It simply states that it must be able to supplement the water-based system(s) in the building.
- NFPA 24 – 3.6 Fire Department Connection. A connection though which the fire department can pump supplemental water into the sprinkler system, standpipe, or other water-based fire protection systems, thereby supplementing existing supplies.
NFPA 13-2019 Standard for the Installation of Sprinkler Systems, simply extracts that language and uses the same definition found in NFPA 24 for FDC’s. NFPA 13-2019, in Section 16.12.3 Fire Department Connection Types, allows for the use of thread-less connections, as an FDC, with the only requirement being that the connection must be listed for that use. They also clarify, in the appendix A.126.96.36.199, that an FDC is only intended to supplement sprinkler demand and not intended to deliver a specific volume of water.
- 3.74 Fire Department Connection. A connection though which the fire department can pump supplemental water into the sprinkler system, standpipe, or other water-based fire protection systems, thereby supplementing existing supplies. [24, 2019]
- 188.8.131.52 The use of thread-less couplings shall be permitted where required by the authority having jurisdiction and where listed for such use.
- 184.108.40.206 The purpose of the fire department connection is to supplement the water supply but not necessarily provide the entire sprinkler system demand. Fire departments connections are not intended to deliver a specific volume of water.
NFPA 13 clearly allows the use of thread-less quick connect large diameter style Fire Department Connections. There are also no requirements for volume, as they are only required to supplement the system. This would lead to the conclusion that the use of large diameter quick connects with fire sprinklers is acceptable without the need to justify any flow requirements.
NFPA 14-2019 Standard for the Installation of Standpipe and Hose Systems, on the other hand, takes the requirements a step further. It defines FDC’s in two separate definitions for automatic and manual standpipe systems. The first definition is for automatic standpipe systems, stating the connection is used to pump secondary water supply at the required system demand and that it can also be used to supplement an existing water supply.
- 220.127.116.11 Fire Department Connections for Automatic Standpipe Systems. A connection though which the fire department can pump secondary water supply to an automatic standpipe system at the required system demand. Supplemental water can also be provided into the sprinkler system furnishing water for the fire extinguishment to supplement existing water supply.
The second definition for manual standpipes which takes on the responsibility of being the primary water supply at the required system demand.
- 18.104.22.168 Fire Department Connections for Manual Standpipe Systems. A connection though which the fire department can pump the primary water supply to a manual standpipe system at the required system demand.
Both definitions make it clear that FDC’s used for both manual and automatic standpipe systems shall provide the system demand.
NFPA 14 also allows the use of large diameter hose connections in the system requirement Section 22.214.171.124. While a standpipe system is hydraulically calculated, the FDC is sized to meet that system demand. NFPA 14 gives that sizing guidance to the flow, in the installation of standpipe and hose systems chapter, Section 7.12.3 for 2 ½ inch inlets, requiring them to be sized to provide 250 gallons per minute of flow. The allowance of the large diameter inlets in Section 126.96.36.199 however does not provide sizing requirements other than stating they shall be of size to accommodate the required flow.
- 188.8.131.52 The use of thread-less couplings shall be permitted where required by the AHJ and where listed for such use.
- 7.12.3 Fire department connections sizes shall be based on the standpipe system demand and shall include one 2 ½ in. inlet per every 250 gpm.
- 184.108.40.206 An approved large diameter hose connection of a size to accommodate the required flow shall be permitted.
In the absence of sizing requirements in the standard, designers may utilize the individual product specification sheet and/or the listing requirements. Product specification sheets consistently show that the thread-less quick connect large diameter style FDC provides a water flow range of 500 – 1000 gallons per minute-per inlet but fails to give specific flow guidelines. They also clearly show that only 4-or-5 Inch connections are listed for use as an FDC.
The UL’s listing requirements for thread-less connections describes in, UL-246A, Outline of Investigation for non-Threaded Connections for Hydrants and Fire Department Connections, does not provide any specific flow limitation, it does however include some of the performance requirements as described in NFPA 1963, Standard for Hose Connections.
While the current edition of NFPA 14 does allows the use of thread-less quick connect large diameter style fire department connections in standpipe application, it does not however provide the guidance needed for system design sizing in the same manner currently provided for the standard traditional 2 ½ inch fire department connection inlet.