NFPA 25 - Water Flow Requirements

[safetyeveryday]

Hello All,

Are there specific water flow requirements for an NFPA 25 fire protection system that is installed within a general purpose assembly (e.g., an auditorium)? If so can you please provide some information.

Thanks for your help in advance!

Mitch

 

[stookeyfpe]

NFPA 25 governs inspection, testing and maintenance of water based fire protection systems and will not contain any criteria for water flow requirements.

What exactly are you seeking: fire flow, the required discharge density and design area for an automatic sprinkler system, etc.?

 

[safetyeveryday]

I'm trying to outline the proper water flow requirements for an FPS.

Thanks for the expeditious response.

 

[cdafd]

Are you located in the US?

If so is this project on a military base?

 

[safetyeveryday]

Yes in the US...no, not on a military base.

 

[MatthewJWillis]

You are looking in the wrong book.
All 25 is concerned with is IF water will flow, not how much.
For that information you will need NFPA 13 and a qualified contractor to perform calculations, that is if the hydraulics placard is not there.
If there is a required hydraulics placard at the main System Riser, the information you are seeking will be there. (red sign 4"x6" or so, attached to System Riser)
The information will be for that building/system only. Each one is different.

There are ways to "guess-timate" what is required, but it would be just that....

R/
Matt

 

[cdafd]

Guess last question

New system to be installed or existing system?

 

[safetyeveryday]

New system

 

[TravisMack]

Likely a light hazard area. Base design is 0.1/1500 + 100 gpm hose allowance for light hazard. However, if you have sloping ceilings, the design area could be 1950 sq ft. If you have a dry system and sloping, the design area could be 2535 sq ft. If you are in a combustible concealed space, it is likely you will be limited to 120 or 130 sq ft per sprinkler. This will cause over-discharge due to minimum pressures. So, that could increase your flows. If you are in a ceiling under 20', you could reduce your design area as much as 40%. If the system is a tree, you are likely to have as much as 20% over-discharge due to friction losses and higher pressures at sprinklers closer to the supply in the design area. If you have a gridded system, you are likely looking at 5-10% over discharge. A dry system will have a C-factor of 100 vs a wet system with C120. This will likely cause a greater amount of over-discharge from the sprinklers. Are there specific insurance requirements that will modify these things mentioned above? Are you using extended coverage sprinklers.

These are the kinds of things you need to be looking at. That is why there is no way for people on a forum to provide a real answer to this. It will be very specific to the job.

As the wise old man, Matt Willis, pointed out, anything provided here would be a "guesstimate" and because of the variable I stated above, it could be way off. A wet system in a 10' ceiling could be roughly 100 gpm from the sprinklers. A dry system in a very cut up attic could be as much as 500 gpm demand from the sprinklers. See how wide the range is.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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