NFPA 13 Minimum pipe size for pilot line detectors

I have previously used 1" pipe as pipe size for pilot line detector lines for deluge systems. However in figures for deluge systems of cooling towers in the Annex (A. thru, it indicates 1/2" pilot line.

Has anyone seen anything that would specify NFPA 13 minimum pipe size for pilot line detectors?


In the 1000’s of deluge systems I have inspected they all used 1/2" pipe.
All that pipe is doing is holding air, making it bigger does not help. Air empties from the pipe deluge valve trips, simple as that.

Above is a snippet.


What a great reply. When someone has seen 1,000’s, you have to admit they know their stuff. Thank you for being so helpful to others and using forums to learn and share.