Can a hydrant flow test (for the purposes of a fire sprinkler design) be conducted using a single hydrant?
If so, how is this actually done? Is it recommended? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
15 Comments
Dan Wilder
11/29/2023 07:38:56 am
NFPA 291
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Glenn Berger
11/29/2023 08:08:31 am
Dan gave an very good detailed answer. In Summary:
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Anthony
11/29/2023 08:27:16 am
I agree with Glen and Dan here.
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sean
12/31/2023 06:55:12 pm
the one hydrant method throws so much into that one point makes an issue that I really don't trust the numbers that come from it.
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M. Newell
11/29/2023 08:19:14 am
AFSA just put out a posy about this on linkedin/facebook. It can be used to verify capacity of the hydrant but should not be used as a water supply evaluation. I would recommend following them on social media they have good informative posts about questions they get.
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Alex
11/29/2023 01:22:53 pm
Agreed! I just read that. Highly recommended.
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Chris
11/29/2023 08:30:17 am
If you are doing a flow test and by yourself, there are ways to do this and still flow 2 hydrants. What I have "heard" before was to use your phone to video the test hydrant while you flow the other. Then you can review the video after to determine the before, during, and after pressures.
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Dan Wilder
11/29/2023 08:41:54 am
I've done this several times....just make sure that when you start the recording and set the phone down, you don't turn the recording off or the phone isn't angled to pick up the gauge or being pointed into the sun AND you check the recording prior to packing up....or plan on redoing the test (practice makes perfect I'm told...)
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Jesse
11/29/2023 08:35:56 am
Dan is on the money here.
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Casey Milhorn
11/29/2023 08:49:51 am
Yes, can be done and sometimes it's your only option. Will everyone accept it, no. Would I do it for an ESFR system, or other high demand system, no. Would I do it for sizing a fire pump, no. Would I use it for a residential or light hazard project, yes, but only if that was the only hydrant available. Also, there are situations where the city doesnt have reliable info on their system arrangement, closed valves, etc and the gauge or flow hydrant can't be verified if on the same system/zone. In this case I do a one hydrant and a two hydrant test and compare results. I really think the most important thing is to use commonsense in all situations, do your homework, and cover your tail. If you or your team doesn't understand the purpose and nuances in performing a flow test, stick to the book and ask someone if you run into a new situation or have concerns.
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Jack G
11/29/2023 09:03:56 am
Agree that it is a bad idea.
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11/29/2023 09:21:19 am
Just to clarify, NFPA 291 is a recommend practice, and not a standard, so there is a grey area.
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James Art, FPE
11/29/2023 10:33:33 am
Perhaps you can get the static somewhere else that is close ?
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Fred Walker
11/29/2023 08:51:28 pm
Let add my concurrence to everyone above.
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Chris
12/1/2023 02:26:49 pm
I would say a single hydrant should not be used for supply analysis if there are other options. Videoing a static/residual gauge is easy to do. There are some people that will recommend gauges that are digital with a "minimum pressure" recall feature to obtain the residual pressure on the gauge hydrant. But after evaluating that, against a regular gauge that is being observed, the "recall" gauge will read a lower pressure than what is observed on the regular gauge after the pressure settles once all the water is moving, and in my experience it can vary between 5% and 20% of a difference. So I used to tell guys it was fine for doing a pre bid flow test for estimation purposes but for the actual design it wasn't to be used.
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