Originally Posted by oldred
Black iron pipe is steel however the fittings are usually cast iron these days and of poor quality, I saw one 1/2" coupling that was so chocked down inside it would flow less than a 1/4" fitting. These fittings are safe to use as long as they are not welded (rarely done anyway) but they may be very hard to seal and can even be porous. Good quality fittings are getting harder to find and even though they too are cast they are cast steel not cast iron (straight fittings are made from steel pipe not cast), cast steel fittings are usually stronger than the pipe, have clean cut easy to seal threads and can be welded if needed. Go to a real plumbing supply not a McHome store for fittings and insist on quality fittings, stay away from any fitting that says CHINA on it!
Stay away from the 7 sided Russian pipe too, even China pipe is rounder than it is.