As always it comes down to specific situations and judgement. From an ITM standpoint tie-in drains are incredibly valuable as they significantly reduce the likelihood of one drain out of many getting missed and causing a system break. Take a theoretical open warehouse dry system where the riser and cross main happen to be on the high side of a shed roof, and you have 20 branch-lines all pitched down to the low eave (don’t laugh, I’ve seen it before). Tying them all together into a single low-point might cause water delivery times to skew, but if you instead divided them into four or five drain clusters then you will have significantly improved the maintainability of the system while minimizing the “gridding” effect.
The commentary can also be misleading if you only skim the first paragraph and don’t take time to digest the whole context. The commentary leads with a comment about how the drain should be at least 1” in size. This could easily be misinterpreted as meaning that the tie-in piping should be at least 1” in size since that is what this code section is about. This reading would suggest a benefit in increasing the piping to a larger size which would be in direct conflict with the code section. It’s not till the very last sentence that the commentary reiterates why 1” is the max size permitted. The commentary it trying to provide some helpful context about the hydraulic effects of tie-in drains, but the structure does make it seem like the author is saying the code section shouldn’t be followed. Here is my humble attempt to improve the clarity of the commentary. Based on my personal opinion of the intent obviously. “When two or more adjacent branch lines are trapped in a dry pipe or preaction system, the ends of the branch lines must be piped together utilizing 1” pipe and run to a single low point drain. at least 1 in. (25 mm) in size, as stated in 16.10.5.3.5<https://link.nfpa.org/publications/13/2022/chapters/16#ID000130002180>. The drain section after the tie-in piping should be sized per the requirements of 16.10.5.3.5 needs to be equipped with a valve and a nipple and cap or a valve with a plug to facilitate moisture removal from the system. Properly pitching tie-in drains and removing condensate from drains prior to freezing weather are extremely important measures. Typically, tie-in drains consist of smaller-size piping connected to a rather large volume of piping, and, with these smaller drains, freeze-ups are possible. Care should be taken when determining how many branch lines are tied together to a single drain, Tie-in drains on multiple adjacent branch lines should be avoided, if possible, because the use of tie-in drains, in effect, creates a gridded system. Gridded dry pipe systems and gridded double interlock preaction systems are prohibited by 8.3.2.7<https://link.nfpa.org/publications/13/2022/chapters/8#ID000130000804>. In these types of systems, all the air in the piping must be evacuated before a steady flow of water is discharged from the operated sprinklers. A gridded pipe arrangement is likely to result in excessive time delays before effective sprinkler discharge occurs. Tie-in drains are considered necessary to allow rapid drainage of systems protecting cold environments. While The restriction that tie-in drains be limited to 1 in. (25 mm) should help minimize delays, dividing the branch lines into smaller groups each with an individual drain manifold may be necessary when a significant number of adjacent branch lines are present.” Hope this helps! Eric Rieve Rieve Fire Protection From: [email protected] <[email protected]> Sent: Monday, March 13, 2023 7:53 PM To: 'Discussion list on issues relating to automatic fire sprinklers' <[email protected]> Subject: [Sprinklerforum] Re: Combining dry system drains Now that is interesting… The wording of the code is that tie-in drains are required, but the commentary says they should be avoided if possible. The 2022 edition (16.10.5.3.6) has the same wording in both the code and the commentary. David L. Miller, P.E. Engineered Fire Protection, LLC 11920 Richcroft Avenue Baton Rouge, Louisiana 70814 225-273-5040 From: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> Sent: Monday, March 13, 2023 6:41 PM To: [email protected]<mailto:[email protected]> Subject: [Sprinklerforum] Re: Combining dry system drains 2016 edition NFPA 13 8.16.2.5.3.6 ….. commentary from handbook…..Tie-in drains on multiple adjacent branch lines should be avoided, if possible, because the use of tie-in drains, in effect, creates a gridded system Jeff Normand From: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> Sent: Monday, March 13, 2023 6:37 PM To: 'Discussion list on issues relating to automatic fire sprinklers' <[email protected]<mailto:[email protected]>> Subject: [Sprinklerforum] Re: Combining dry system drains NFPA 13 (2016 edition) 8.16.2.5.3.6 Tie-in drains shall be provided for multiple adjacent trapped branch pipes and shall be only 1 in. (25 mm). Tie-in drain lines shall be pitched a minimum of 1⁄2 in. per 10 ft (4 mm/m). David L. Miller, P.E. Engineered Fire Protection, LLC 11920 Richcroft Avenue Baton Rouge, Louisiana 70814 225-273-5040 -----Original Message----- From: Sean Lockyer <[email protected]<mailto:[email protected]>> Sent: Monday, March 13, 2023 6:31 PM To: [email protected]<mailto:[email protected]> Subject: [Sprinklerforum] Combining dry system drains Can dry system drains (I.E. - Drum drips) be combined or interconnected ? Sean Lockyer Project Designer AITLifeSafety _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org To unsubscribe send an email to [email protected]<mailto:[email protected]> _________________________________________________________ SprinklerForum mailing list: https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org To unsubscribe send an email to [email protected]<mailto:[email protected]>
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