NFPA 25 Standpipe Test with Only 2 Standpipes?

4/8/2022

I have a hospital that has two "double hose valves" at the top of two different standpipes on the roof. One is on a helipad and the other is below on a different roof. Both are the most remote locations.

Per NFPA 25, for the 5-year test, I'm supposed to flow 500 gpm at the most remote then an additional 250 gpm at a different standpipe until I reach 1,000 gpm for the fully-sprinklered building.

Can I just flow 500 gpm out of both double-hose valves (2 standpipes), or do I have to flow 500 gpm, then 250 gpm, then 250 gpm using three different standpipes?

Thanks.

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11 Comments

Alex

4/8/2022 06:06:27 am

Hi,

The Sprinkler Contractor you have conducting the test should already have an SOP written outlining their steps in conducting the test.

First. do you only have two standpipes within your building? From your last sentence, it alludes to there being more than two. NFPA 25 (2014) states standpipe system demand shall include 500 gpm from the first standpipe and 250 gpm for each additional standpipe until the total system demand is simultaneously flowing.

If you are uncertain about design flow, NFPA 14 (2013) states that maximum flow rate shall be 1000 gpm for buildings that are sprinklered throughout and 1250 gpm for buildings that are not.

Lastly, both valve locations will not be the most remote. The most remote location is a single point of your standpipe system that requires the greatest pressure to produce adequate flow. This is typically the highest valve since the pressure loss due to gravity is more significant than friction loss. EXCEPT, this is not always the case, especially if valves are located one story down than the others and are installed across the entire building… Hydraulic calculations can tell you which hose valve will be considered the most remote.

Hope this helps.
Alex

Nick

4/11/2022 07:39:38 am

Alex is spot on here. Also note you'll need a minimum 100 psi at that most remote standpipe connection.

Glenn Berger

4/8/2022 08:07:59 am

In order to comment, a full schematic of the system will need to be provided. You can possibly do a series of tests to ensure that the system can flow the required quantity of water.

Jesse

4/8/2022 09:08:39 am

I'm not sure where the 1,000-gpm flow rate is coming from. You should flow 500-gpm, 250-gpm from each of the two most remote hose connections of the most remote standpipe. and then 250-gpm from each remaining standpipe to a maximum of 1000-gpm for sprinklered buildings. Since you only have 2 standpipes, its 500-gpm + 250-gpm for a total flow of 750-gpm.

Colin Lusher link

4/8/2022 10:10:18 am

Your demand is 750 gpm with only two standpipes, not 1000 gpm. You need to flow 500 gpm from the most remote standpipe, then 250 at most remote valve on each additional standpipe up to a maximum of 1000 gpm. If there is only one additional standpipe, then you only need to flow 750 gpm. If you had three standpipes, you'd need to flow 1000 gpm.

Alex, yes, there is only one remote standpipe, but the second valve flowed should be the next most remote or demanding. We understand what he's saying here.

Dan Wilder

4/8/2022 11:13:40 am

Yep, flow is only 750GPM when there are only 2 standpipes in the building, 3 or more would require the full 1000 GPM (assuming a fully sprinklered building). As for testing, technically you could get away with flowing only 2 standpipes at 500GPM each would be a worst case scenario (again, assuming the other standpipes only have one hose valve at the top of each) but would not follow the 500250/250 standard already within NFPA 25.

The additional hose valve at the helipad is pretty common for the couple I have done(many times when there are no foam monitor nozzles).. Having a hose manifold (2 hose valves) at each main roof level with stairwell access is not uncommon as well with specifications

Are there any previous test reports showing what was done and accepted?
Do you have any calc plates or design drawings indicating what was remote? Even with the two levels of double hose valves, really need to understand the physical layout.

Anonymoose

4/8/2022 01:24:35 pm

So from reading Glenn's and Dan's comments, I have a question

4 3 2 1
Supply ═╩══╩══╩══╝

(assume the actually layout doesn't make (SP) 2, 3, or 4 more remote by distance or height)

Lets say SP3 was difficult to flow, ie no or deficient drainage, would it be acceptable to pickup an extra 250 on SP2 and get your required 1000 gpm that way? Since it would be more hydraulically demanding to skip 3 and make the feed carry 1000gpm all the way to 2, I think so.

PS. I think question does imply least a third standpipe

COLIN LUSHER

4/8/2022 01:55:22 pm

Technically, NFPA 14 requires you to flow each of the four standpipes in this situation. There is no provisions for the arrangement you/Glenn/Dan are suggesting.

But practically? Yes, I would say this would be a decent alternative way to test the system, you'd just need to get the buy in from the AHJ or approving authority since this scenario isn't covered by NFPA 14.

Anonymous

4/9/2022 09:32:20 am

This is a fully sprinkled hospital with multiple standpipes.
The two standpipes near helipad are the most remote. Both standpipes have “Siamese” hose valves at the top of each one at roof.
I also have another standpipe that I am prepared to flow at ground level and run hose out door to the parking lot to get an additional 250gpm.

Previous flow tests have only been with one hose monster at most remote standpipe(definitely not correct).

This system has a high pressure fire pump. After fire pump is an 8” pressure reducing valve. I recently adjusted it properly(was dropping well below 100psi while 2” main drain was open. It is now at 175psi with 2” main drain fully open.

I’m going to reach out to AHJ but in this area I don’t believe I’m going to get much help. Also going to dig into calcs more.

Thanks for all the advise!

COLIN LUSHER

4/11/2022 11:13:20 am

Ahhhh, ok, understood. In that case, yes, you'll need to flow 1000 gpm to properly test the system. It would be reasonable to ask the AHJ to allow you to flow the two most remote standpipes at 500 gpm each in lieu of adding in 250 gpm from a 3rd standpipe. Even though that differs from NFPA 14, it would be more demanding test and should satisfy the AHJ, in my opinion.

Anonymous

4/11/2022 08:47:01 pm

Thank you.

NFPA 25 Standpipe Test with Only 2 Standpipes?

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