I tell folks that lead has not been an approved piping material for gas distribution for many, many decades. The joint methods are no longer acceptable either. There's good reasons it's not done that way anymore. I don't care if it's worked fine up to this moment - replace it. Lead piping was used from the very first natural gas well to the street lights in Fredonia, NY in 1821. In 1870, Rochester, NY was supplied with NG through bored pine logs with iron bands.