Which type of pipe is often referred to as 'black iron pipe'?

Black iron pipe is commonly referred to due to its dark, rust-resistant finish that is created during the manufacturing process. This type of pipe is primarily made from steel, which is welded or threaded for various plumbing and heating applications.

The primary use of black iron pipe is in gas lines and water supply systems, as it provides excellent strength and durability under pressure. Additionally, its ability to handle high temperatures makes it suitable for both residential and commercial use.

Other types of piping, such as galvanized pipe, feature a zinc coating to prevent rusting, while plastic pipe is made from materials like PVC or CPVC, which are not metal at all. Cast iron pipe, although also a type of iron pipe, is significantly heavier and is primarily used in drainage and sewer applications rather than in gas lines. Thus, steel pipe is the correct identification for what is commonly known as black iron pipe.