Recently, the  technical committee removed the requirement for check-valves to be installed in interconnected standpipes in the NFPA 14 2024 edition. This article will discuss the reasoning behind this decision, as well as what this could mean for the future of the standard.

Why Did the NFPA 14 Technical Committee Remove the Requirement for Check-Valves in Looped Systems?

For many editions, the standard has required check-valves to be installed at the base of each standpipe to prevent the circulation of water in looped standpipe systems.  The substantiation by the committee for the change reverses this position and indicates a benefit in looped systems with allowing water to circulate through the most advantageous path.
The removal also has a clear benefit to reducing friction loss and the need for inspection, testing and maintenance of the valves, previously required under NFPA 25 Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems.

Design Criteria

The question is whether this hydraulic benefit extends to the required design criteria for standpipes. With the removal of one-way check-valves, it opens the discussion: can combined flows be used in calculating the requirements found in Section 10.2 and 10.6 for pressure and flow.
10.2.6.1 Minimum Design Pressure for Hydraulically Designed Systems. Hydraulically designed standpipe systems shall be designed to provide the waterflow rate required by Section 10.6 at a minimum residual pressure of 100 psi at the outlet of the hydraulically most remote 2 1⁄2 in. hose connection

10.6.1.1.1 For Class I and Class III systems, the minimum flow rate for the hydraulically most remote standpipe shall be 250 gpm through each of the two hydraulically most remote 2 1⁄2 in. hose connections on the standpipe.

Currently, Section 10.6.1.1.1 states that the calculation is done “on the standpipe” indicating the most restrictive path but is this necessary in a system that is interconnected? One argument would be that it needs to be calculated for a worst-case scenario, but then what is the hydraulic benefit to the removal. Secondarily, what is the overall hydraulic significance in allowing the combined flow to be utilized in the design.

NFPA 13 and Looking Ahead to NFPA 14 2027

NFPA 13 Standard for the Installation of Sprinkler Systems allows the designer to take advantage of looped sprinkler systems which provide a better hydraulic characteristic than a single supplied tree design. Does this add to the argument to allow combined flow to be considered in the design or is this hose connections and sprinklers.

The easier water moves within a system the better the system will perform, but the question remains and hopefully, as we move forward into the 2027 edition of the standard, we can continue to advance the design and address this if needed.

More about the Author:

Terin Hopkins has 34 years of experience in public safety and is currently the Manager of Public Fire Protection for the National Fire Sprinkler Association. He represents NFSA on many NFPA and UL technical committees, including NFPA 14 Standard for the Installation of Standpipe and Hose Systems.

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