Join Galvanized Pipe to Copper PipeUpdated: Jun. 10, 2019
Prevent metal pipe corrosion with special dielectric nipples
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Stop galvanic corrosion
Photo 1: A badly corroded joint
This dielectric fitting didn’t provide enough separation between the dissimilar metals, allowing the pipes to corrode and clog.
Whenever you join copper water lines to galvanized steel pipe, you should be concerned about the corrosion caused by joining two dissimilar metals, called “galvanic corrosion.” An electrochemical reaction occurs that causes the steel pipe (in this case) to rust and clog up. The dielectric fittings commonly available in home centers (Photo 1) have a short plastic nipple that keeps the metals from touching, but the metals are still close enough to cause a reaction and corrosion anyway.
The solution is to use a special 3-in. fitting called a “dielectric nipple” (Photo 2). They’re available for about $9 at plumbing supply stores. A plastic liner (3 in. long) inside the fitting keeps the metals far enough apart so corrosion won’t occur (as much!).
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- Pipe wrench (2)
- Tube cutter
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- 3-in. dielectric fitting
- Copper female adapter
- Copper slip fitting
- Galvanized pipe
- Pipe thread sealant