Save on Pinterest

Join Galvanized Pipe to Copper Pipe

Prevent metal pipe corrosion with special dielectric nipples

FH06OCT_JOIPIP_01-2Family Handyman
Install 3-in. plastic-lined nipples between copper and steel pipes to prevent galvanic corrosion from clogging the water line. It's a quick, easy fix.

You might also like: TBD

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.

Photo 2: A 3-in. dielectric nipple

The 3-in. plastic liner in this dielectric fitting provides a greater degree of separation to keep the dissimilar metals from corroding.

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