Components of a Return Bend
A return bend is the piping arrangement for pendent sprinklers where piping stems from the top of the branch pipe (riser nipple), runs horizontally (arm over), and then down to the sprinkler (drop).
Raw Water Sources, Mill Ponds, Open-Top Reservoirs
Where Not Required
So Why Use Return Bends?
1. Sediment Accumulation
Things to Consider
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Minnesota Public safety Issue | Link
NFPA 13 | Link
8/5/2016 11:44:22 am
Nice pictures. You should make more.
Janet A. Washburn, CFPS, FM, MIFireE, MS
8/6/2016 07:17:11 am
Excellent article and I appreciate the time spent with the code references! The pictures are very helpful. I just shared this article with hundreds of peers in Florida.
12/2/2016 06:00:14 pm
Your drawings rock, love to see more.
5/11/2017 08:19:00 am
The exact references to the NFPA codes are very helpful. Great stuff!
6/12/2017 06:15:37 pm
Thank you very much. I have just started to do sprinkler shop drawings and this made it very clear why concealed heads are installed on return bends
7/5/2017 03:34:00 pm
I like how you said that this kind of fire sprinklers prevent mineral deposit. With how important a fire sprinkler system is you definitely do not want something like a hard water deposit blocking the flow of water during an emergency. Getting a system that will allow you to do minimum upkeep and maintenance will also help you save time and money, allowing you to focus on your business.
1/20/2018 08:59:55 am
When flex drops replace hard-piped return bends, how are they commonly installed--- coming out from the top of the pipe, side or bottom?
2/17/2018 05:47:41 am
In general, flexible drops can be installed from any direction; however, side tapping or tapping from the top of the branch pipe does prevent sediment accumulation just as the return bend does.
2/6/2018 08:55:09 am
Is it necessary to connect the branch from the top of the mains with a spool or can direct branches be taken from the side when clean water sources are used.
I see branch lines connected directly to to the sides of mains all the time in clean(er) water situations. Mains typically have caps at the end of the pipe for inspection and potential flushing in part to help clear deposits if there are any.
4/20/2018 01:13:06 pm
Hey, what to do if outlet is 1/2" with upright directly on outlet, how you arm over theN???
10/9/2018 07:11:17 am
There are "street elbows" that have a male 1/2" thread to a female 1" outlet. Just be careful as these are typically only allowed in retrofits and they must be hydraulically calculated. NFPA 13 addresses these in more detail.
4/24/2018 02:52:44 am
The is any minimum requirement for the length of the drop without support. Sometimes we came across the installation where sprinkler drop more than 2 mtrs without support. I am looking for the support requirement for the drop.
6/14/2018 11:33:10 am
9/27/2018 04:41:21 am
We connect our branch line below the cross main pipe due to the structure beam. If we lower the cross main, the pipe will be exposed below the ceiling so we connect it that way. NFPA 13 only specify that sprinkler should have return bends and should be connected on the top of the branch pipe ,but im not sure if the branch pipe should be connected on the top of the cross main. Please enlighten me on this issue. Thank you so much
10/9/2018 07:10:01 am
Branch pipe is typically run at the same level or above the main so that the system can be drained.
10/12/2018 04:43:15 am
Mr. Meyer, thank you so much for answering my question.
10/12/2018 07:01:38 am
It may not be in the short term, but draining the system will be necessary to fix any leaks, make any changes to the system, or to inspect the pipe interior.
1/18/2019 05:08:10 pm
That is a good point that you should use return bends to prevent mineral deposits from happening. It would be good for a fire sprinkler not to have sediment accumulation. That way when there is a fire, the sprinklers won't malfunction.
4/6/2019 02:45:48 am
simply superb explanation....
4/22/2020 04:14:06 pm
Is there any reference out there about the maximum length of the horizontal section of a return bend / arm-over? I don't see one in NFPA 13, but may be missing it. Reason to ask, have an installation where the pendent sprinkler is attached to a ~6-ft long arm-over
4/23/2020 07:13:30 am
6/17/2020 01:45:35 am
Hi Joe Meyer,
6/23/2020 05:12:36 am
Comments are closed.
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Joe Meyer, PE, is a Fire Protection Engineer out of St. Louis, Missouri who writes & develops resources for Fire Protection Professionals. See bio here: About