Hey Sully!
What's that tank holding?
I'm no expert in petro tanks but DbigKahunna sure is FWIW...
I know there's API 570, 650 and probably others but, like I said before, Dbkahunna's the man to talk to here!
These might be standards instead of a code but, I'm not 100% on that and Kahunna or Giovanni would be the ones to ask about that... Then again, Al could too!
Then there's the American Water Works Association General Steel Tank Committee, Steel Water Storage Tanks: Design, Construction, Maintenance, and Repair.
Here you go Sully! Take your pick:
http://www.awwa.org/store/standards.aspx?Category=STAND&Subcategory=STORAGEThis one covers steel water pipe:
http://www.awwa.org/store/productdetail.aspx?ProductId=6820Respectfully, (For the most part!
)
Henry