Is it necessary for the Fire sprinkler black steel pipes to be UL listed although it is conforming with ASTM A53 standard as per NFPA 13 188.8.131.52.? If the answer is yes, in which code can I find such information?
There is no requirement for materials or components to be "UL Listed", simply listed by an organization that is acceptable to the AHJ. Commonly this could be UL but there are other agencies which provide testing, certification, and listing.
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