Have a situation I've never crossed before: we have a very small building that's getting expanded. Originally the sprinkler contractor gave two options for the general contractor to price their underground fire sprinkler service - (1) is to provide a 2-1/2" main, the other (2) is to provide fire barriers in certain areas with automatic door closers to allow the room design method be used, and bring in a 2" underground.
I completely recognize that small underground pipe is not good practice and limits the future potential of the building. We recommended a 4-inch underground, but the increased cost for tap fees and underground pricing added $10-15,000 to the job which the owner adamantly refused.
We were given notice to proceed with 2-1/2" underground and thus provided a 2-1/2" riser and 2-1/2" mains.
The GC gave a different direction for the underground and pulled 2" underground and is providing fire barriers and automatic door closers.
We've recalculated using the room design method and everything still works with the 2" underground, but the 2-1/2" riser and 2-1/2" main is already ordered and on the way to the jobsite.
Does NFPA 13 have any restriction against having a larger riser or main size than the underground?
Because of the change in building construction, we only need a 2" riser and 2" main but will instead already have prefabricated 2-1/2" in both. My thought is to have a permanent placard clearly affixed to the riser showing the situation and clearly identify on as-builts the methodology used.
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