Fire Hydrant OFF ESFR GRID

[Robert Gardner]

I have a 6x4 gridded ESFR sprinkler system with 2" or 2 1/2" branch lines.
The GC decided not to run the underground main around the building to the hydrant.
he wants me to run the hydrant off the 4" floating main or the 6" feed main over to the incoming 6" underground that supplies the hydrant.
I have run independent bulk mains across buildings too feed wall hydrants before.
The system is feed with a 95 psi 1500 gpm pump. IF I add 250 gpm at the hydrant connection point on the grid, increase the lines to 2 1/2" the grid works. (ESFR 250 Hose demand)
The 250 gpm hose would be my normal total hose demand requirement. (50 gpm each hose drop 150 gpm outside hose)
QUESTION: Would the 250 gpm outside hose to the hydrant be correct.
The hydrant would then have Pump pressure.
The hydrant would be controlled by the system riser valve and the hydrant shut off.
Could the hydrant be considered hose allowance.
My other option is to run a separate main ahead of the pump to the underground (hydrant), have a separate main for the ESFR system.

 

[cdafd]

Is there city or some other approval authority,,

That has blessed this??

 

[cdafd]

Can you post a simple plan

 

[TravisMack]

If I understand the scenario, you could possibly do that with AHJ approval. It seems you may need to feed this with 6". You could come off the 4" float main and run 6" to the point where you go underground or to the wall hydrant. I would add my 250 gpm hose at that point. Afterall, the hose allowance is typically added at the nearest hydrant. However, you will also need to prove that the hydrant can meet the minimum requirements of the site fire flow. Has anyone considered the requirement for site fire flow. Based on what you describe as your pump, it should not be an issue. But, hydrants are not just 250 gpm hose allowance devices. If I had the say, I would probably want a separately valved bulk run, similar to a standpipe. That way, you can shut down the sprinkler system and hydrant independently of each other.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[Robert Gardner]

Drawings are still in the design phase. Our state plan review is a rubber stamp joke.....all about the money, fire marshal is AHJ with every little knowledge of fire protection design (except the ones that attended a two week course, there experts).
The building is 160,000 SQFT with four ESFR systems, the pump is located on the east side of the building with a hydrant off of the 8" lead-in, the other hydrants are on the far northwest and southwest side of the building (supplied by 6" UG, connected to ESFR system).
The underground feeding the hydrant is 6" and I'm feeding the UG with 6" main.
The developers must have worked out the hydrant location with AHJ, one on east side of the building off 8" Lead-in, one the northwest side and one on the southwest side of the build (precast building, hydrant located 60ft away, one and half time wall height).
PS Our state has only adopted the 2010 addition of NFPA.

 

[Robert Gardner]

Where would you find minimum require site fire flow. I looked thru NFPA 24 and only found reference to Master Stream (250 gpm) Chapter 9).

 

[MatthewJWillis]

Annex B of the IFC.. I think that's it..

 

[TravisMack]

Yes, Annex B of the fire code. It is likely a minimum of 1500 gpm @ 20 psi. However, it could go up depending on size of bldg and type of construction.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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