Typically when I work on campus/multi-building systems, I am using a single underground main and splitting off to each building. Since you don't have to consider a multiple building fire problem, we have typically worked on the hydraulically most-remote building for underground sizing and use wall PIVs to offer individual building shutoffs, with FDCs on the individual buildings.
I'm getting challenged on "what allows this in code?" It's mostly a question of - where is the limit on how long a loop can be? I'm looking at this from a sprinkler design perspective and whether each individual building's sprinkler system is able to perform hydraulically. Is the limit for the length/layout/sizing of a campus underground loop simply the more demanding of Fire Flow or sprinkler system feeds? Is there a code basis for this? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
11 Comments
Glenn Berger
4/26/2024 08:10:06 am
A few questions requiring answers must be considered prior to a proper response to your question be given.
Reply
Casey Milhorn
4/26/2024 08:39:42 am
No issue with it. Typically the issue has more to do with arrangement, placement of backflow, FDC placement strategy, fire pump placement (if required), and whether or not you have private hydrants on this line. If you have private hydrants, fire flow demand may be required to be met at these hydrants. Additionally I have ran into some local AHJs that have minimum size requirements on underground lines that feed hydrants based on number of hydrants and/or distance to hydrant.
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Franck
4/26/2024 08:48:15 am
Limitation for size and length is directed by the hydraulic calculations. As long as you can supply all systems with a given pipe diameter and loop length, it is fine.
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Pete H
4/26/2024 09:00:00 am
None I can think of. Circulating street mains are typically gigantic compound loops or grids.
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Ricardo Gonzales Jr
4/26/2024 09:10:15 am
1st determine what the building needs for a proper system without and with a fire pump. Then direct the Civil folks to make that occur. Unless you're designing a private system, FPs usually don't get involved in water supplies.
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Jeyson Ventura
4/26/2024 09:12:45 am
A different perspective on why the length of the loop system may be getting challenged.
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Blaine
4/26/2024 12:36:37 pm
Might look into AWWA manual M31. Distribution System Requirements for Fire Protection.
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Mark Harris
4/26/2024 02:17:50 pm
All great responses. May want to look at fire flow requirements in the appendix of the IFC IBC as well.
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Jack G
4/26/2024 04:26:02 pm
Couple things.
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Todd E Wyatt
4/30/2024 08:03:09 am
Scoping Codes (e.g. IBC-2024) and their referenced standards (e.g. NFPA 13-2022) include prescriptive requirements (e.g. shall) for the Design Professional to meet when designing a building and/or one of its systems. Some of these requirements include restrictions (e.g. "Sprinklers under walkways shall NOT be spaced more than 8 ft (2.4 m) apart horizontally.) but these are far less frequent than the use of "shall" without "not" following it.
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J.H.
4/30/2024 02:10:58 pm
Generally, the governing Utilities Dept. will have guidelines regarding dead-end water mains, esp. those supplying hydrants and/or fire protection systems.
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