What Is a Dielectric Union?
A dielectric union is a plumbing connector that joins dissimilar metals while limiting electrical current between them. The fitting has insulating material between its connection points. This design helps reduce galvanic corrosion where copper tubing connects to steel parts, such as a water heater tank or threaded steel pipe.
Quick Facts About Dielectric Union
Category
Metal-separation plumbing fitting
Used for
Water heater pipe connections
Common confusion
Not a valve or leak control device
Also called
Dielectric Fitting
Often discussed with
Water Heater Installation
Key Takeaways About Dielectric Union
- The insulating barrier separates dissimilar metals.
- The fitting joins threaded plumbing connections.
- A dielectric union is not a shutoff valve.
How Dielectric Union Works
A dielectric union joins two pipe sections with different metals. One side connects to each pipe, and an insulating washer or sleeve separates the metal surfaces inside the fitting.
Related glossary terms: Anode Rod, Compression Fitting, Expansion Tank.
The union still creates a watertight path for the plumbing system. Its insulating parts interrupt the electrical path that can form between dissimilar metals in contact with water. This helps limit corrosion at the connection.
On a water heater, the fitting may connect copper supply piping to a steel tank connection. The union also lets a plumber disconnect the pipe without cutting the line.
Expert Note
When we install a water heater, we check the connection materials and the union's sealing surfaces. We also confirm that the insulating parts sit correctly and that the joint stays accessible for future service.
Dielectric Union in Practice: A Real-World Example
A new water heater has steel threaded connections, while the home's supply lines use copper. A dielectric union can join each material at the water heater connections while helping limit corrosion at the joint.
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Related Terms
Anode Rod
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Compression Fitting
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Expansion Tank
An expansion tank is a small pressure-control vessel connected to a closed hot-water system. It gives…
Water Heater Element
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