Best Practice for Flushing of Gridded System?

1/22/2021

Regarding fire sprinkler system flushing of a wet-pipe gridded system; NFPA 13 Section 16.6.4 “All branch lines on gridded systems shall be arranged to facilitate flushing”.

We are doing a project which has more than 50 branches in a gridded system.

Do all these branch lines need to be provided with a flushing capability? How is this commonly achieved?

FM Global data sheets say to provide a small nipple between two flexible couplings, assuming removal of the nipple to flush the lines. Are there alternatives to this?

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5 Comments

Mike

1/22/2021 09:08:07 am

I usually design tailbacks on grids and on those put a tee and plug, grooved add-a-cap, or grooved cap beyond the last head.

CJ Bonczyk

1/22/2021 11:03:25 am

A future accepted proposal from NFPA Technical committee meeting will be removing this section from NFPA 13 due to its impracticality. This will be removed from the future edition.

Public Input No. 307-NFPA 13-2019 [ Section No. 16.6.4 ]
16.6.4
All branch lines on gridded systems shall be arranged to facilitate flushing.

Statement of Problem and Substantiation for Public Input

"Delete this section. By the nature of the design of gridded systems, the carry lines are connected to cross mains which facilitate flushing. Many designs of gridded systems use outriggers to the outside of the cross mains. This requirement for flushing is impractical."

In my humble opinion I would say that a remote inspector test on the furthest branchline along with a grooved cap with flushing connection on the remote main will suffice assuming AHJ approval as well.

Fred Moore

3/22/2022 08:34:58 am

What if there was a sprinkler head adapter with a spring loaded valve that shuts off the flow when the head is removed. You would
1 remove the head shutting off the flow
2 insert a nipple with a valve
3 flush line
4 remove the nipple and valve
5 reinstall the head
All without turning the water off at the main valve. If interested please contact me.
Thanks

Dan Wilder

1/22/2021 11:29:10 am

Is the flushing due to known obstructions or just to comply with the "ability" to flush?

Typically, most branch lines can comply with this via grooved piping fab (end cap or Adacap can be removed). In the case of threaded tailbacks or threaded ells into the main, providing a threaded tee with a plug (in lieu of the ell) would comply but be careful with pipe reductions to restrict available flow conditions for the largest pipe size along the BL). A coupling before the secondary (dead main) main to break the BL's from the RN's would also suffice.

Annex D of NFPA 25 has some good reading on the process and gives some insights to what is needed to perform the activity if needed.

Pete D.

1/22/2021 11:57:16 am

2 1/2" hose on the remote capped end of the float main for 15 minutes.

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Best Practice for Flushing of Gridded System?

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