From my AHJ perspective and in regards to flexible drops and tenant improvements, where you typically don't receive hydraulic calcs, how are you then accounting for their equivalent lengths and friction loss?
I know some AHJ's require new calcs whenever these are being used period. I'm interested to see how others handle this. Thank you! Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
15 Comments
Dan Wilder
1/13/2025 07:06:21 am
All of our AHJ's require calcs if there were no flex hoses previously on a project as there are so many options and lengths for the hoses that exceed what the hard pipe eq. length was originally.
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NK
1/13/2025 08:27:57 am
Our AHJs also require calculations for flex hoses where hard pipe was originally designed and installed.
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[WSF] Dan Wilder
1/13/2025 08:33:44 am
I will also add that we are also required to match or beat the flex hose characteristics that are installed so we can't just use any flex hose (typically length restrictive). The inspectors are a little hit and miss with enforcement but it's getting more consistent.
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Pete H
1/13/2025 07:25:44 am
In my human opinion:
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Glenn Berger
1/13/2025 08:16:37 am
It all depends on the extent of the retrofits and if the water supply conditions are different.
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D
1/13/2025 09:15:55 am
Where we are adding flex drops to a system where there previously were none, where the existing system is old and no hydraulic calculations are available- I understand the need for calculations. Example- we did a grocery store where the overhead was scheduled and we added a ton of flex drops and calculated them and had to use fewer max bends to make them work. This example makes sense to me.
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Anthony
1/13/2025 10:11:44 am
I think calc's are required every time. 20-some-odd feet of extra 1'' pipe is a lot for who knows what kind of sprinkler. If I have a system with an original safety factor of 2 psi it won't work with flex heads. Alternatively, if the system has a 20 psi safety factor and its ~10 sprinklers I could be convinced with a good contractor not to require calcs. But this all depends on the original design.
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Jack G
1/13/2025 10:13:25 am
If the heads are/ were center of old tile - pattern, usually the AHJ in my neck of the woods will not make you recalculate as long as the head spacing doesn’t change dramatically.
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Jerry
1/13/2025 10:46:02 am
As an AHJ, we do require the calculations on a finish out where no flex drops were used prior except when using the new VS-2's. I review plans as well as do inspections here. And I would require the maximum amount of bends allowed to be calculated because in the field, the installers are not likely looking out to only using 2 bends versus 3 bends. Plus, during an inspection on a large finish out, inspectors might not catch the use of too many bends. I think Victaulic is pretty smart to make this flexible drop.
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CHRIS H.
1/13/2025 11:02:32 am
Thanks for all the reply's
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James E Art Fire Protection Engineer (FPE)
1/13/2025 04:50:36 pm
Flex drops are often reused when the office layout changes,
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Greg Collier
1/15/2025 10:35:58 am
We always require calculations and drawing, you may use existing calculations, supported by a recent flow test with seasonal adjustment. It may require an update drawing and the conformation by the (Licensed) Design Professional indicating that the demand will less than the existing design and available water supply. All this information should be readily available if they are doing proper ITM and maintain record drawings.
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Brian Cook
1/15/2025 08:17:32 pm
Victaulic came out with a flex hose that do not need calculations. It is called the VS-1 & VS-2, one is a dry flex head
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Sean Kostka
1/25/2025 03:12:24 pm
Appreciate you mentioning Victaulic VS1 and VS2 Brian.
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Brian Cook
1/25/2025 04:40:45 pm
Thank you, Sean
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