Hi loggenrock ... sodajerk.
As far as I understand it... By the NFPA's criteria, the National Fire Protection Association's standards--which I do not know if they could be considered statutes, according to NFPA58, I think Chapter 9, in the past there was a rule formulated that propane tanks had to be 12 years old or newer before needing replacement, but there were years grandfathered in, something like anything from 1983 and older. In the last couple of years, the grandfathering clause was ended, and all tanks have to be replaced or certified after 12 years old. Here's the NFPA's link:
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=58#
