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?
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4/8/2022 06:06:27 am
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.
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.
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.
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.
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.
4/8/2022 01:24:35 pm
So from reading Glenn's and Dan's comments, I have a question
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.
4/9/2022 09:32:20 am
This is a fully sprinkled hospital with multiple standpipes.
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.
4/11/2022 08:47:01 pm
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