water demand for 5 standpipes

[rdippm]

Hello,

I am designing a small 5 story building and our fire autority has approve to uso one 11/2" fire hose at each floor. I have calculated pipes using a water demand of 100 gpm at 100 psi at the topmost fire hose. It this correct or do I have to add other demands from the others hoses?

Need to say that where I leave we don´t count with expertise people in this matter. We are doing the best we can but sometimes the codes are difficult to understand so we need help in this matter. Hope understand my English.

Thanks for your help

 

[PEDARRIN2]

I would suggest obtaining the services of an engineer who understands the code.

When dealing with fire suppression, it is not a good thing to try to do it without understanding the codes.

There are just too many things that could go wrong.

 

[DonPhillips]

NFPA 14 is the standard for standpipes adopted by most states. Keep an eye on the edition since each states vary which edition is in force at time of application.

Don Phillips

http://worthingtonengineering.com

 

[SprinklerDesigner2]

DonPhillips,

Georgia is one of them and has the most peculiar I've run across.

http://www.gainsurance.org/ANNOUNCEMENTS/1056AR-1302007151339.pdf

on page 25 Exception 2.

2. Delete 7.8.2.1 in its entirety and substitute in its place the following:

“7.8.2.1 Pipe schedule designed standpipe systems shall have piping sized in accordance with the pipe schedule in Table 7.8.2.1 to provide the required waterflow rate at a minimum residual pressure of 100 psi (6.9 bar) at the topmost 2-1/2 inch (65 mm) hose connection and 65 psi (4.5 bar) at the topmost 1-1/2 inch (38 mm) hose connection.

Exception No. 1: Where the local Fire Chief or local Fire Code Official having fire suppression jurisdiction permits lower than 100 psi (6.9 bar) for 2-1/2 inch (65 mm) hose connections, based upon local suppression tactics, the pressure shall be permitted to be reduced to not less than 65 psi (4.5 bar).

Exception No. 2: Where the building is protected thoughout by a supervised automatic sprinkler system and the building is not a high-rise, as defined in 3.3.9, the minimum residual pressure provisions shall not be mandatory when the standpipe system piping is a minimum of eight inches (8”) nominal diameter.

Exception No. 3: Existing high-rise buildings, as defined in 3.3.9, that are protected throughout by a supervised automatic sprinkler system shall be permitted a reduction of the minimum residual pressure requirement of 100 psi (6.9 bar) at the hydraulically most remote 2-1/2 inch (63.5 mm) hose connection to 65 psi (4.5 bar).”

I wish they would lower the 8" to 6" for standpipes or pipe feeding a single standpipe leaving everything else at 8". At 500 gpm through 8" the friction loss developed is near nothing but the change was well needed. Three and four story hotels all had to have fire pumps and the local authority required these to be diesel or be equipped with a generator backup/transfer switch etc which drove costs out of control. The number of 4 story motels with the top floor at 31' or 32' above lowest level of fire department access, requiring a $100,000 plus standpipe installation, is staggering.

This is just my opinion but I've always felt standpipes could get one into a lot of trouble dealing with standpipes because after sprinklers we view them as simple and easy. Not the case at all.

 

[rdippm]

Thanks everybody for your opinion. I have the latest of NFPA 14 and for me it is pretty clear what to do for hydraulics calculation when using 21/2" hoses, but when using 11/2" hoses it only says that you have to supply the topmost fire hose with 100 gpm at 65 psi and it does not stablish a minimun diameter of pipe (what I think is good).

 

[AbbyNormal]

usally they want 500 GPKM at the remote standpipe and 250 GPM for each additional one

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[mcarewm]

max out at 1250 gpm .

 

[PEDARRIN2]

Isn't the maximum of 1250 gpm for non sprinklered buildings and for sprinklered buildings, it was 1000 gpm?

 

[TravisMack]

PEDARRIN2:

You are correct with the max flows.

Travis Mack
MFP Design, LLC