A dielectric union is a specialized plumbing fitting used to connect two pipes made of different metals, such as copper and galvanized steel. Its internal plastic gasket prevents the metals from touching, which stops the "galvanic corrosion" that occurs when an electric current flows between them. These fittings are a code requirement for Water Heaters and hydronic heating systems to prevent leaks at the connection points. Without a dielectric union, the joint will eventually rust and fail, leading to significant water damage in your home. You can find these and other essential plumbing connectors in our Water-Plumbing collection. Using them is a standard best practice for any professional installation involving ACIq water-based heating equipment. They are a simple, inexpensive way to prevent a major plumbing catastrophe down the road. It is a small part that performs a massive role in protecting the integrity of your home's piping.