Historically, the home’s copper water pipe system provided a safe ground for the home’s electrical system. The plumbing system was grounded because its metal pipes extended a long way underground. However these days the increased use of polyvinyl chloride, or PVC, pipes throughout home plumbing systems displaced the use of copper and other metals enough that water lines were no longer reliable grounds for electrical system.
A secondary electrode is a length of metal, typically 8 to 10 feet, driven into the ground. When correctly installed, only enough of the rod remains above ground for attachment to a heavy gauge wire. The other end of that wire attaches to the home’s electrical system and bonds to the plumbing system. Standard building codes accept steel conduit, steel rods and copper-clad steel as grounding electrodes. These devices are also called secondary electrodes, since some electricians still ground electrical systems to the home’s plumbing. Electrical codes require the use of a second electrode in these instances.
At my old home (built 1935) the electrical panel was not grounded. However, there was a 14 gauge copper wire connected from the Neutral Bus Bar to a galvanized cold water pipe. When we replaced all the old corroding galvanized pipe with Pex piping it was time to pound in an electrode.
The point is the ground you have today may not be a valid ground tomorrow.
