A dielectric union is a type of plumbing fitting used to connect pipes made of different metals while preventing galvanic corrosion. Galvanic corrosion occurs when two dissimilar metals come into contact with each other in the presence of an electrolyte (such as water), leading to corrosion and degradation of the metals.

A dielectric union consists of two parts:

  1. A union: This is a threaded fitting with female threads on one end and male threads on the other end. It allows for easy connection and disconnection of the pipes.

  2. A dielectric fitting: This fitting is typically made of non-conductive material, such as plastic or rubber, and acts as an insulator between the two metal pipes. It prevents direct contact between the dissimilar metals, thereby inhibiting galvanic corrosion.

The dielectric union is installed between the two metal pipes that need to be connected. The threaded ends of the union are connected to the respective pipes, while the dielectric fitting is sandwiched between them. The union provides a reliable and leak-free connection, while the dielectric fitting ensures electrical isolation between the metals.

Dielectric unions are commonly used in plumbing systems where copper pipes are connected to galvanized steel or iron pipes. They are also used in water heaters, water treatment systems, and other applications where dissimilar metals are present.

It's important to note that dielectric unions should be installed following the manufacturer's instructions and local plumbing codes. Regular inspection and maintenance of the dielectric unions are also recommended to ensure their effectiveness in preventing corrosion and maintaining the integrity of the plumbing system.