Understanding hydraulic requirements in NFPA 13D

Blog Post created by freddurso Employee on Oct 15, 2014

Matt KlausA common question we receive through NFPA's technical advisory services for NFPA 13D, Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes, involves the hydraulic calculation of the system. Unlike NFPA 13, Installation of Sprinkler Systems, NFPA 13D does not require full-blown hydraulic calculations that assess friction loss of every fitting and linear foot of pipe.

One of the goals of the NFPA 13D technical committee is to promote the inclusion of systems in both new construction and retrofit installations. As such, requiring a complicated and time-consuming hydraulic calculation procedure would add cost to the project and in some cases may preclude otherwise qualified designers from being engaged with the standard.

NFPA 13D offers two simple approaches to these calculations. These procedures are described in both an eight-step and 12-step process that require limited mathematical computation, while still providing the assurance that there will be sufficient flow and pressure for the particular system being installed.

These calculations are conservative, but are simple to execute and not time-consuming. The time savings can be seen both on the design side and on the plan review side. Reviewing the hydraulics for a 13D system for a municipal plan reviewer is a simpler endeavor than that of the NFPA 13 approach.

Matt Klaus is NFPA's principal fire protection engineer and staff liaison for NFPA 13D. Klaus is a regular contributor to this blog and discusses the technical components of home fire sprinklers.