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I haven't had any experience doing site calculations before, but I'm curious how it works from a practical standpoint. Fire Flow is required by the International Fire Code here locally, and there's guidance (albeit not formally adopted) in Appendix B of the IFC for a total demand. Additionally, there's hydrant spacing requirements for any particular building, and guidance on how far the hydrants can be from a building.
In order to determine how the hydrants are fed (dead-end vs. looped and size of pipe), are there specific flow and pressure amounts that each hydrant has to be calculated at? Is it similar to a standpipe calculations where each hydrant has to have a specific flow? I'm not performing the design work myself, but I'm just curious how that is typically done and pipe size determined. Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
13 Comments
Hector R
5/6/2020 11:54:48 am
Yes, it's done in a similar way as standpipes, hydrants will require 1500 GPM at 20 PSI.
Nick
5/6/2020 11:58:01 am
Where does the 1,500 GPM per hydrant come from? Am I missing that somewhere? 8/3/2021 02:05:11 am
How we calculate the pressure and how we design the pipe line size in sprinkler system
Mike
5/6/2020 12:27:24 pm
Piping size is Chap. 7 of NFPA 24.
Jesse
5/6/2020 12:55:03 pm
Good question. Its not dissimilar to any other volume calc you would do for automatic sprinkler design. I guess the process would depend on which software suite you're using. For a program like AutoSPRINK its pretty simple, but it starts with the fire flow requirement in your local code.
Franck
5/7/2020 10:49:33 am
1500 gpm per hydrant?
Jesse
5/7/2020 12:23:29 pm
Absolutely. I spent 19 years as a career firefighter before fire protection engineering. I could count on one hand the number of hydrants that didn't flow at least 1500-gpm. Right now I'm looking at flow test data that flows 86 static, 85 static @ 1007 gpm. You don't think that's not flowing way more than 1500-gpm as the flow curve progresses?
Bill
5/7/2020 05:40:09 pm
Keep in mind NFPA 13 is for the hose stream allowance, in addition to the sprinkler demand. It has no bearing on the fire flow requirements for a hydrant. The IFC or NFPA 1 give the minimum flow requirements.
Jesse
5/7/2020 12:24:47 pm
That was meant to say 86 static, 85 residual @ 1007 gpm
Shaikh
5/8/2020 04:56:44 am
Even i have concern on pressure requirement for hydrant.
Jesse
5/8/2020 07:38:27 am
Shaikh - I'd look at that specification a little deeper. 20-psi is always our benchmark minimum residual so we don't collapse a main or pull a draught from the suction of a pump. I would speculate that the 100-psi minimum is along the lines of "must maintain a minimum static pressure of 100-psi. So 100-psi static with our rated flow somewhere at a lower pressure, and system not to have a residual pressure lower than 20-psi.
Muhammad Jawad
12/14/2020 12:48:10 pm
JESSE: How to find out the Gpm of fire system? let's say we have 6 hydrants in one system & 15 in another.
Paul
2/25/2022 12:18:23 am
I am researching water supply on two sites in two different states. The 2018 IFC's Appendix B gives the criteria for fire flow. The NFPA 1-18 Fire Code also has this data and table 18.5.4.3 addresses flow. My research indicates that for either major document it's 1500 gpm at 20-psi per fire hydrant within 250 feet of the building's footprint. There is a table that allows the fire flow per hydrant to be reduced on distance from the building. Leave a Reply. |
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