Correct Way to Support Long Sprinkler Drop?

6/1/2020

I have a question id like a second opinion about. I have a client with a new build boat storage facility, approx 30 ft high, at one end on the ground floor is an office area with a suspended ceiling. The installers have used U-Bolt Mechanical Tee couplings to attach the drops to the branch line, and then hung 20-ft of 1" pipe as the drop.

What is the correct way to secure these drops?

There is currently no lateral or vertical support. This is not in a seismic area.

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11 Comments

Dan Wilder

6/1/2020 08:23:42 am

As you reference there is no seismic qualifications...there is nothing in NFPA to require additional hanging if the arm overs comply with the requirements of "Unsupported Lengths" in whatever year is your applicable standard.

This would fall under installer common sense, not NFPA. If the MT are drilled out the same side of the branch line (horizontally), the line will have a tendency to spin due to the offset torque weight of the drops. In this case, best practice would be to provide a tee on the run and cap or at least a hanger between the BL and the ell before the drop on each piece of BL piping (if the BL is grooved) or every other MT for a threaded BL.

If they are drilled vertically from the bottom (poor drills...) and any arm-over occurs at the base of the drop (complying with NFPA for those unsupported lengths) then typically you are OK. If the AO is at the top for some reason, the previous hanging practice would be helpful.

As for any horizontal restraint for the drops, again, there is no NFPA requirement. The drop will have some natural sway available to it but no requirements to brace/restrain it.

mike

6/3/2020 01:24:48 pm

Thanks for taking the time to respond, much appreciated

Casey Milhorn

6/1/2020 10:56:44 am

Dan nailed it. Exactly what I was going to say. Have to watch the weight of the drop "spinning" the line, especially if its grooved above. Also, just the amount of stress being put on that armover is concerning. Definitely a hanger at the armover if it happens up top, nothing if it happens close to the office ceiling.

mike

6/3/2020 01:25:09 pm

Thanks

Shane

6/1/2020 11:39:52 am

I would suggest installing a mechanical tee close to the wall, drop down then arm over to the sprinkler head location for the office. Then you have the option to strap to the wall for support and hang the armover from the deck or steel above. I would especially use this method if there were many drops being supplied from above.

mike

6/3/2020 01:25:49 pm

Thanks for the feedback - good options

Mike

6/1/2020 01:15:22 pm

No requirements for restraint but that's a lot of pipe for a mechanical tee. Might end up needing a Tee, nipple and cap to the closest joist for hanging.

mike

6/3/2020 01:26:23 pm

Just doesnt look right ! Gives me cause for concern

Dale

6/5/2020 09:34:41 am

In the past, where we had large areas, we would install a new main at the lower ceiling level, tapping off of the main above, and use branch lines or arm-overs from that new main. While your work is already installed, this method may work for you in a future project.

George Naill

6/22/2023 10:11:50 am

So what if the drop is 35' and we are in a seismic zone D. We have a builder who is erecting tilt buildings with 40' minimum clear height to the bottom of the Girders, sprinklers are another 5 feet higher. Office areas have 10 to 11' ceiling to top of framing. The UPC for plumbing stipulates that metal threaded piping used for water supply be supported at every other floor but not to exceed 25' of vertical pipe. how does that or would it apply to Fire Sprinkler Supply. A few of these warehouses have been completed prior to my arrival with no support, they just hang down 35' form a short 12" or so long arm over. I'm Not a Fire Inspector yet but will be picking this up at some point once get the certifications.

I definitely think using the installer common sense approach doesn't work here. This is a seismic zone and if a 30' length of W36x 97 column un restrained during the 6.9 Nisqually quake was able to oscillate nearly 4' in diameter then an unrestrained 30+ foot sprinkler line is going to oscillate significantly more and if the only attachment is to the brace is a ceiling grid there is a high likelihood of the sprinkler pipe failing and punching through the ceiling.

Thoughts

Mike link

12/22/2023 12:20:21 am

What about a 1" x 9' wet system riser, do to removed drop ceiling replacing a pendent with an upright on a vertical pipe straight up 12" below metal roof deck. Does this have to be braced somehow to the open web I-beams or ? Please Advise............

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Correct Way to Support Long Sprinkler Drop?

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