Steel to Copper Fittings

About Copper Fittings

• Copper fittings come in three standard sizes: 1 inch, 3/4 inch and 1/2 inch. These fittings are made out of pure copper and are designed to work with any thickness of pipe, as all pipes contain the same diameter pipe threads regardless of thickness. Copper fittings must be soldered, or sweated, into place using solder, flux and a blow torch. Copper fittings are highly resistant to corrosion and can be used with either hot or cold water.

About Steel Fittings

• There are two types of steel fittings. Black pipe is simply steel that has been painted black. It is among the least resistant to corrosion and will rust over time. Black pipe is not rated to carry potable water inside homes, so it's usually used in irrigation or drainage applications. Galvanized steel has been treated with zinc and is more resistant to corrosion. However, galvanized steel will still rust over time and is not rated to carry drinking water.

Joining Copper to Steel Fittings

• It is possible to join copper and steel fittings together. While the materials are different, a transition union will allow you to connect steel to copper or vice versa. The union contains a copper ring on one side that is sweated to the copper pipe using traditional flux and solder. The other end contains steel pipe threads that allow you to screw the steel pipe into the union. Similar unions are available for other materials, such as PEX pipe or PVC.

The Importance of Dielectric Unions

• When joining copper to steel, it's important to use a dielectric union. A dielectric union is the same as most other types of union fittings, except that it also contains a small rubber washer that sits between the two types of pipes. The washer creates a physical barrier that prevents the copper from electrically touching the steel. It's important to separate these materials because when they come in contact, a very low-voltage electrical current is allowed to flow between the metals. This occurs because almost all water is slightly acidic or basic, which creates an electro-galvanic action between the metal materials. The washer prevents the connection from completing, thus preventing the associated corrosive action that would otherwise eat away at the union.