What Is the Difference Between Copper Plumbing vs. Steel Plumbing?

Steel Was Early Plumbing Pipe

• Steel and its relative, cast iron, once were common in plumbing. The first plumbing pipe was iron, but steel gradually replaced iron because of steel's superior strength. Standards were developed for steel pipe dimensions and connections, such as threads for couplings to join two pieces of pipe together, and it was a basic plumbing pipe. Steel pipe is frequently called "iron pipe" and some suppliers even list "IP" in catalogs.

Copper Is Tubing

• Copper pipe is more correctly called copper tubing, because pipe is generally a material that can be threaded, and copper is connected without threading. Two pieces of steel pipe are connected by screwing a threaded male element into a receptive threaded female element. Two pieces of copper pipe or tubing are connected with solder or some type of threaded connector, usually brass, which expands the ends of the copper to make a secure joint.

Steel Is Strong

• Steel pipe is sturdy and typically has thick walls. It has great "burst" strength, which is the ability to withstand internal pressure. It remains stable at high temperatures, making it suitable for fire protection sprinkler systems and similar applications. Galvanizing or coating it with zinc improves its resistance to rust and corrosion.

Copper Is Flexible

• Copper pipe or tubing does not rust and is naturally resistant to most corrosion. It is more compact than steel and is much more flexible, so it can be bent or formed around corners and obstructions. It comes in coils, so long lengths of copper tubing can be installed without joints. It is easier to connect, so two lengths or T type joints can be secured in several ways. It is easier to cut than steel pipe and much lighter to transport and handle on a job site.

Both Have Plumbing Uses

• Both copper and steel have applications in plumbing. Copper is used more frequently for household water supply because of its easier application and resistance to corrosion. Steel is used for non-potable water or major water distribution systems that require larger pipes. Most copper pipe or tubing is 6 inches or less in diameter; steel pipe can have a diameter of a foot or more.