John,
I believe you may be confusing oxidation with electrolysis. There is a link below that describes electrolysis in detail.
http://www.multimedia-sa.gr/olympic-...rolysisen.html
Salt, or any conductive medium, can cause oxidation. Electrolysis is the result of a reaction between dissimilar metals, not pvc or plastic. You could also call your local plumber and cheak with him or her.
Jim L