Fire Water Pipe Size & High Flow Building 1

[andy_oohhh]

I am designing the fire water system for a 6 story apartment building with cellar and bulkhead roof in NYC. It is light hazard and from the chart on NFPA-13, the density is .1 gpm/sf and area is 225sf. That gives me a sprinkler flow of 22.5 gpm. After laying out the sprinklers and taking consideration of max/min spacings and areas with exceptions, I have a total of 94 sprinklers. Total flow is 2115 gpm which seems very high. Also, the client advised me that the maximum pipe size that the city will allow from there 8" main is a 4" pipe and they will not allow multiple taps. With the amount of flow calculated, that pipe size won't be possible. Which leads me to think that I am doing something wrong when calculating the flow. Any advice?

 

[goutam_freelance]

Refer chapter 19 of NFPA 13. There are rules for calculating minimum water supply requirement. It may not be sum of all sprinkler flows. Hydraulically most demanding sprinkler zone demand may be used with consideration for adjacent zones.

 

[Artisi]

Simply solution is to give it to someone qualified to design the system.

 

[LittleInch]

My guess is that you don't have to allow for all 96 sprinklers to be active all at the same time.

But NFPA regs can be complex and need some experience to navigate.

 

[UFT12]

The criteria for LH per NFPA 13 call for an application (or design) area of 1500 sf, not 225 sf. There are specific requirements about the definition, shape and location of the application area that defines the flowing sprinklers. See chapter 27 or 28, depending on version, of NFPA 13. You will end up with way less sprinklers.

 

[TravisMack]

Simply solution is to give it to someone qualified to design the system.

This is the best answer.

 

[TravisMack]

I am designing the fire water system for a 6 story apartment building with cellar and bulkhead roof in NYC. It is light hazard and from the chart on NFPA-13, the density is .1 gpm/sf and area is 225sf. That gives me a sprinkler flow of 22.5 gpm. After laying out the sprinklers and taking consideration of max/min spacings and areas with exceptions, I have a total of 94 sprinklers. Total flow is 2115 gpm which seems very high. Also, the client advised me that the maximum pipe size that the city will allow from there 8" main is a 4" pipe and they will not allow multiple taps. With the amount of flow calculated, that pipe size won't be possible. Which leads me to think that I am doing something wrong when calculating the flow. Any advice?

I believe you have asked this across multiple different sites. The answer is that you really need a good mentor to teach you fire sprinkler system layout and design. You don't calculate all sprinklers flowing at once. You need help better determining your area of coverage per sprinkler. You could probably choose different sprinklers and get your design area down to 4 sprinklers.

Fire sprinkler systems are not rocket science and are not overly complex. However, there are a myriad of requirements you must follow and be familiar with. You don't want to just jump blindly into it and take on projects where you have no understanding or experience, without a good mentor helping you along the way. For some training in the layout of fire sprinkler systems, consider taking the 10 week Accelerated Design Training course offered by sprinkleracademy.com.