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NFPA 13 requires dry pipe and preaction system branch piping to be pitched at least ½” per 10 ft, and mains pitched at least ¼” per 10 ft in non-refrigerated areas.
Should an exception be considered (less pitch or no pitch) for systems utilizing nitrogen to maintain system pressure? Submitted anonymously and posted for discussion. Discuss This | Submit Your Question | Subscribe
3 Comments
Tim D
8/17/2020 10:23:42 am
No an exception should not be considered. Although nitrogen is being used and should prevent condensation from forming in the piping, don't forget that dry and preaction systems are still subject to full flow testing per NFPA 25 (as long as they don't protect refrigerated areas). Even on alternate year partial trip (or partial trip for refreigerated spaces), it is still possible to introduce some water to the piping during testing. The pitch of the piping is needed to make sure that any water introduced in the system can drain properly. Also don't forget that in the event of a system actuation from a fire we still need to be able to drain the water from the piping following the event to restore the system to service as quickly as possible.
Mike
8/17/2020 12:30:31 pm
There could also be an accidental opening or purposeful actuation of the valve which would require draining it. The pitch requirements are not only for condensation.
Rob B
8/18/2020 09:32:25 am
No exception, how do you intend to remove water after testing or activation. Ideally, it is generally a bad idea not to install all pipe without some little bit of pitch to help water drain properly, and to a low point as intended. Just because its fire sprinkler doesn't mean basic plumbing 101 shouldn't be considered. Leave a Reply. |
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