Standpipe system working pressure definition has changed over the last few editions of NFPA 14 Standard for the Installation of Standpipes and Hose Connections. The original intent was to clarify maximum system working pressure, exclusive of surge pressure but inclusive of system design pressure required at the fire department connection (FDC). Simply speaking, the working pressure is the anticipated design pressure needed to meet system demand and must be included in the complete design aspect, including the FDC.
While the intent of why the defined term was originally added has remained, the definition was incomplete, and the clarifying of the definition over several cycles has continued to confuse those that use the standard.
NFPA 14 -2016
The term, “system working pressure” first appears in the 2016 edition and states that maximum pressure applied to a standpipe does not include surge pressure. This was stated to help understand that a system working pressure is needed to correctly apply hydrostatic test pressure at acceptance, but the definition specifically excluded FDC pressure in the language which leads to confusion over the requirements for an FDC. Is FDC pressure part of the system, designed to system demand pressures, and if excluded, what requirements do they have to meet?
NFPA 14 -2019
The 2019 edition modified the language and struck the exclusion of pressure from the FDC. The committee stated that the FDC piping is subject to hydrostatic test requirements at acceptance and should not be included within the language of system working pressure. This further leads to additional confusion with understanding the system working pressure requirements for FDC. If not included, what is the system working pressure for the FDC and what design criteria do they have to meet?
NFPA 14 - 2023
The 2023 edition of NFPA 14 has proposed to once again modify the language aimed at correctly defining the intent of the original defined term. At the first draft meeting a proposed First Revision No. 60 looked to correctly define the term system working pressure. This definition was unanimously passed by the NFPA 14 Technical Committee and is now in the Public Comment phase of the standard adoption cycle. It states that maximum anticipated pressure (static and residual) applied to a standpipe system component, exclusive of surge pressure and inclusive of the system design/demand pressure from the FDC. This clarifies the need for all components, including FDC’s are required to meet the working pressure requirements of the design.
This brings us back to the original intent to exclude surge pressure but also provides the designer language to better understand that all components, including the components of the FDC, must be designed to meet the anticipated working pressures required to meet system design.