that is NOT black iron. December 6, 2015December 6, 2015 francain01 saw this at a house where new gas lines had been run. 20′ farther to outside wall where black iron nipple came in from meter. CSST black sheathing isn’t even a conductor, but at least they tried to ground it. Attached Images Advertisements Share this:TwitterFacebookGoogleLike this:Like Loading... that is NOT black iron.