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How to Transition Galvanized Steel to Copper

March 23, 2021 Viega
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There are 43 quintillion possible configurations of the Rubik’s Cube. That’s only a few more than the number of pipe-to-pipe combinations a contractor is likely to face on the job.

Knowing the correct method for joining dissimilar materials is one of the most challenging things for a contractor to learn. Depending on the nature of work (residential, commercial, industrial), a plumbing contractor is likely to encounter a dizzying variety of materials: copper, different types of PEX, galvanized steel, stainless steel, brass, PVC, CPVC, cast iron and ABS.

Particularly in older structures, a contractor is likely to find a mix of piping materials, often the result of repairs or incremental upgrades, rather than complete system replacements.

Problems occur when dissimilar metals are joined without consideration to their compatibility. Whenever two different types of metal come into contact with each other or an electrolyte (like tap water), one of the metals might begin to corrode. That’s why joining dissimilar metal pipes requires using the correct insulating transition fittings.

While there are general rules of thumb to follow, the best way to ensure compliance is to consult the local code book. Different jurisdictions have different rules.

Joining copper to galvanized steel

One of the most common metal-to-metal joinings is copper to galvanized steel in potable water systems. Galvanized, which was common in houses built before 1960, is susceptible to corrosion and is now being replaced with copper or other material.

This is one of those joinings that requires protection against galvanic corrosion. We recommend a transition fitting called a dielectric union. This has a threaded steel female pipe fitting on one end, which is threaded onto the male threads of the galvanized steel pipe. The other end has a female copper hub fitting, which slides over onto the copper tubing. Insulating components prevent the two metals from touching.

Viega offers a bronze ProPress dielectric union with an EPDM flat gasket and sealing element for sizes ½" to 2". We also have ProPress adapter flanges in bronze and copper for sizes 1" to 4".
Minimizing Galvanic Corrosion
For more information regarding joining dissimilar metals and transition fittings please contact a technical support specialist at 866-838-8714 or

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