Sprinkler Water Requirement

[PrakMS]

I have a basic question about sprinkler water requirement.

Say for a building that i'm going to construct as per NFPA standards i have arrived at 1000 sprinklers for the facility in total and also assuming that the sprinkler design density is 0.6 gpm/ft2 per 2000 Sq.ft with K-factor 115 sprinklers.

Now should the water tank be big enough to cater to all 1000 sprinklers or should it be considered for certain percentage of the total nos.

Thanks for the help in advance.

 

[TravisMack]

Fire sprinklers do not act like they do in Hollywood. Density x Design Area x water supply duration.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[PrakMS]

@Travis: i did not understand the first part about "sprinklers do not act like they do in hollywood"

Anyways as per your second line, assuming the area protected by the 1000 sprinklers is 8000 Sq.ft and the density is 0.6 gpm/ft2 and the duration is for one hour,
am i right in saying that the water requirement (theoretically) is 288000 gallons(1090 m3).

Pls correct me if i'm wrong.

 

[LCREP]

Park,

You have no clue what your are doing and a internet board is not the place to design a sprinkler system, seek professional help.

Travis gave you the answer to your question "Density x Design Area x water supply duration".

Density= .60
Design area= 2000

.60 x 2000 = 1200 GPM. The actual number will be higher depending on the system layout, this is for estimate only, it could be 5-10% higher.

If this is a NFPA designed system the duration is 120 mins

120 x 1200= 144,000 gallons.

Interior hose stations and any fire hydrants would need to be added to the 144,000. At minimum 500 GPM x 120 = 60,000 gallons

144,000 + 60,000 = 204,000 gallons

 

[PrakMS]

LCREP,

You are right in saying that i have no clue about the system, i'm just trying to understand the system requirements without much of background in fire systems. My problem is that i have to check the outputs given by a consultant and i really got confused when i started reading NFPA.

Anyways coming back to your answer on the water requirement, how does the size/area of the building affect the water requirement. what you have done is taken design density X design area for the chosen density X duration. won't the water requirement vary according to building size, in above equation the building area doesn't come into play at all..

Thanks

 

[LCREP]

Park,

The sprinkler system will control or extinguish if designed and maintained properly. As such NFPA only requires the sprinklers in the design area to be calculated regardless of the size of the building and the number of sprinklers in a building.

Read this report on the experience of sprinklers and how many activate during a fire.

http://www.nfpa.org/research/report...afety-equipment/us-experience-with-sprinklers

From the above NFPA report.

Usually only 1 or 2 sprinklers are required to control the fire.
When wet-pipe sprinklers operated, 88% of reported fires involved only 1 or 2 sprinklers. For dry-pipe sprinklers, 73% involved only 1 or 2 sprinklers.

 

[TravisMack]

It doesn't matter if your building is 2000 or 2,000,000 sq ft. The demand is based on design area. If you are designing based on the sprinklers containing a fire to 2000 sq ft, what does it matter the rest of the size of the building.

Do you realize that not all sprinklers go off at the same time....like in Hollywood movies. (unless you have a deluge system)

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com