The standard for fire flow testing and marking of fire hydrants, NFPA 291-2019: Recommended Practice for Fire Flow Testing and Marking of Hydrants, has been revised.
The current edition, which replaces and supersedes the 2016 version of the standard, is distinguished by including the metric formula for discharge through circular orifices. Further aligning with this change to NFPA 291-2019, the table on discharge through circular orifices has been updated to provide measurable velocity pressures in the metric system.
Water might fall from the sky and occupy 71 percent of the earth’s surface, but its natural abundance isn’t enough to combat fires in society that may range from the mildest flames to the most profound conflagrations. The practicality of fire hydrants is just common sense. In fact, it is illegal in most cities and states to park a car in a manner that obstructs access to fire hydrants.
On the federal level, regulations call for a fire main system to “have enough fire hydrants so that each accessible space may be sprayed with at least two spray patterns of water” (46 CFR 108.423), “be of sufficient number and so located that any part of the vessel, other than main machinery spaces, accessible to persons on board while the vessel is being navigated and all cargo holds may be reached with at least 2 streams of water from separate outlets, at least one of which must be from a single length of hose” (46 CFR 95.10-10), and to comply with several other requirements that ensure their effectiveness and reliable use.
As a voluntary consensus standard, NFPA 291-2019 covers fire flow testing and marking of hydrants. Fire flow tests on water distribution systems exist to determine the rate of flow available at various locations for fire-fighting purposes. For flow testing, the American National Standard outlines guidelines for rating pressure, the determination of discharge, use of pumper outlets, and any necessary equipment or practices for carrying out these procedures and calculating their results.
With the flow testing results, hydrants are classified in accordance with their rated capacities. According to NFPA 291-2019, these classes include Class AA (1500 gpm), Class A (1000-1499 gpm), Class B (500-999 gpm), and Class C (less than 500 gpm).
In accordance with NFPA 291-2019, public hydrant barrels are to be colored their characteristic chrome yellow. However, this does not apply to cases in which another color has already been adopted. The tops and nozzle caps are also painted under a capacity-indicating color scheme to provide simplicity and consistency. This scheme consists of Light Blue (Class AA), Green (Class A), Orange (Class B), and Red (Class C).
Please note that NFPA 291-2019 is a voluntary consensus standard, and users of NFPA standards should consult any applicable federal, state, and local laws and regulations.
NFPA 291-2019: Recommended Practice for Fire Flow Testing and Marking of Hydrants is available on the ANSI Webstore.