We have a project that has a combination standpipe. Due to an issue
with the AHJ interpreting the minimum sizing for a combination
standpipe, we have installed the standpipe as 6". This is a project
designed per NFPA 13R. Each floor control valve coming off the
combination standpipe is a 2" floor control valve assembly (b'fly valve,
check valve, flow switch, gauge, test-n-drain). The test-n-drain is 1"
per NFPA 13R. Each 1" drain line ties into a common drain riser. The
common drain riser was indicated as 1¼" and approved this way. Now, the
inspector is stating that is has to be a minimum of 2". They are
stating that since it is attached to a standpipe "riser" that is larger
than 4", the drain riser must be 2".
I believe this is an incorrect rationale and that technically a 1" drain
riser would be acceptable because NFPA 13R only says that you must do a
minimum of 1" drain. The drain was upsized to 1¼ because of the
requirement in NFPA 13, but it is technically not applicable.
What is the general forum consensus on this? Is a 1¼" common drain
riser acceptable because it is connected to 1" floor control drains.
Or, is the common drain riser required to be 2" because the floor
control assembly is connected to a 6" standpipe?
It would not have been an issue earlier, but all drain risers are installed.
--
Travis Mack, SET
MFP Design, LLC
2508 E Lodgepole Drive
Gilbert, AZ 85298
480-505-9271
fax: 866-430-6107
email:[email protected]
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