For decades, galvanized steel piping has been used extensively in the plumbing industry for its strength and corrosion resistance.
But when it’s time to replace or expand part of an older plumbing system, homeowners and contractors can face a large choice of a key question: which metal is safe and effective to connect to galvanized pipe?
Making the wrong connection can lead to corrosion, leaks, or costly damage. This article is all about what you should and shouldn’t do when connecting other metals, specifically copper, to galvanized pipe.
Understanding Galvanized Steel Piping
Galvanized pipe is a steel pipe that has been coated with zinc to help prevent corrosion. Before copper and PEX became popular, it was a popular material in water supply lines. The interior will never rust or corrode but may deteriorate if exposed to hot–cold (expansion contraction) cycles or if installed improperly when connected to dissimilar metals.
Connecting Galvanized Pipe to Copper: Proceed with Caution
Many plumbers today face the challenge of joining galvanized pipe to copper, especially in older homes. But doing so incorrectly can induce galvanic corrosion. This happens when you join two dissimilar metals (like copper and galvanized steel) directly, especially when they are exposed to water, which is an electrolyte.
Safe Way to Connect Copper to Galvanized Pipe
You could protect against corrosion with a dielectric union, a special fitting that keeps the two different types of metal apart with a non-conductive barrier. This prevents the electrochemical reaction that leads to metal breakdown with age.
Common Metals and Their Compatibility with Galvanized Steel
Here’s a helpful guide comparing different metals commonly considered for connecting to galvanized steel piping:
| Metal | Is a direct connection safe? | Recommended Solution |
| Copper | ❌ No | Use a dielectric union to prevent galvanic corrosion |
| Brass | ⚠️ Sometimes | Compatible in limited cases; dielectric union still preferred |
| PEX (with fittings) | ✅ Yes | Use brass or plastic transition fittings approved for both |
| Stainless Steel | ⚠️ Sometimes | Can be used with a dielectric fitting or an approved transition |
| PVC/CPVC | ✅ Yes | Use threaded adapters or transition couplings |
Additional Tips
- Thoroughly clean threaded galvanized pipe whenever you fit it with new materials, and consider fitting metal with metal.
- Use pipe thread sealant or Teflon tape rated for metal pipe.
- For big jobs or older plumbing systems, have a local plumber check to see which of the two is the easiest and safest one for your specific project.
Wrapping Up
Connecting new piping to an old galvanized steel pipe isn’t as simple as screwing in the next piece, particularly when you’re replacing a section of copper pipe with a galvanized one. You can avoid that by using the proper materials and knowledge, such as using a dielectric union and compatible materials, and having a non-corrosive plumbing system that will last for years. Whether you are upgrading small segments or overhauling entire plumbing lines, understanding how you should transition will help avoid potential issues in the future.
Looking for expert help sourcing materials such as dielectric unions, galvanized fittings, and copper adapters?
Work with a trusted metal supply professional to make sure you have the right ones that form a secure conductive connection.
