Dielectric fittings are specialized plumbing connectors designed to join two dissimilar metals, most often copper and galvanized steel, while preventing the damaging effects of galvanic corrosion. When metals with different electrical potentials touch each other in the presence of water, a small electric current flows between them. Over time, that current causes one of the metals to corrode, leading to leaks, restricted water flow, and costly repairs.
How They Work
A dielectric fitting contains a non-conductive barrier, typically a plastic or rubber sleeve combined with insulating washers. This barrier breaks the electrical path between the two metals, stopping the galvanic reaction. The result is a long-lasting connection that protects both sections of pipe.
Common Applications
- Water Heater Connections: Copper supply lines often connect to a steel tank. Dielectric unions keep the joint corrosion-free.
- Copper to Galvanized Transitions: Older homes may have galvanized steel piping. When upgrading sections to copper, dielectric fittings provide a safe transition.
- HVAC Systems: Chilled water and hydronic heating loops frequently use dissimilar metals and need protection.
Installation Basics
Installing a dielectric fitting is similar to installing a standard threaded union. Key steps include:
- Clean and prepare the pipe threads.
- Apply a suitable thread sealant.
- Hand-tighten, then finish with wrenches, following the manufacturer’s torque recommendations.
Benefits
- Extends the life of plumbing systems.
- Reduces maintenance and the risk of hidden leaks.
- Maintains water quality by preventing corrosion particles from entering the flow.
Bottom Line
Whenever a plumbing system joins copper and steel, a dielectric fitting is an inexpensive safeguard against galvanic corrosion. By isolating the metals electrically, it preserves the integrity of the entire system and saves time and money on future repairs.