DIY with education.If Propane (LP), a copper line is acceptable in most areas for underground as it won't oxidize from the LP.But Black pipe will. Codes are for this reason. Which I am surprised it was permitted.check this out:»www.propane101.com/lpgasserviceline.htm--Splat
Not sure what you are saying. In this installation copper was used underground and black pipe inside a building. What are you saying is wrong with that?