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We have a project with a very large Water Storage Tank that requires a 20" suction line from the tank to the suction manifold side of (3) pumps.
Per NFPA 20, at the connection point from the water storage tank to the supply line to the fire pumps as required by NFPA 20 (2019 ed.) 4.16.6.5, where the pump and its suction supply are on separate foundations with rigid interconnecting pipe, the pipe shall be provided with strain relief in Figure A.6.3.1(a). We can find no manufacturer that has a 20" UL/FM strain relief connection. We do, although, have a supplier that makes a 20" Flexible Double Expansion Joint, but not UL/FM Listed. Does anyone know of any other options, or can we just use this flexible expansion joint and get a waiver from the Fire Marshal and EOR? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
6 Comments
Franck
8/15/2025 08:34:29 am
2 groove couplings on the suction side is sometimes accepted by AHJ.
Rich
8/18/2025 01:47:59 pm
I understand the code interpretation, it is more about finding a solution for the large 20" suction size. We already have to put pilings in for the foundation on the 650K gallon tank, so our concern is whether flexible couplings will have enough axial deflection over time on the separate foundations. Many of our vendors have said they do not seek UL / FM listings for these large sizes as they are not often used. If it were 4" up to 12" we would not have an issue.
Ken Thackery
8/15/2025 10:28:40 am
Where is this project located?
Rich
8/18/2025 01:53:38 pm
Not sure why location matters, but it is in Iowa. Above ground tank, approx. 650K Gallons. Not really a spec to follow on this as it is owner direct, but the owner hired a FP Design firm who missed this in their preliminary plans so we submitted an RFI and they agreed, strain relief would be required. Metroflex whom we would normally use will not make a listed flexible coupling for this size.
Jack G
8/22/2025 05:05:54 pm
The UL/FM part means that it is tested and approved for situations like a pump and tank being on different foundations, or eq zones where there is greater probability of earth movement.
Mark Harris
9/29/2025 01:09:14 pm
May not be room but have seen a couple of 90 degree elbows used as a swing joint. Of course grooved with flexible couplings. Leave a Reply. |
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