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Thread: Copper and Galvanized lines in contact?

  1. #1

    Default Copper and Galvanized lines in contact?

    Late 40's house - replumbed to copper. Outside the service entrance, I've found a maze of buried new and old lines, with a number of copper and (out of service) galvanized lines laid across each other in direct contact. The galvanized lines show significant corrosion where they're in contact with the copper lines, and of particular concern is a still-in-service galvanized natural gas line in firm contact with a copper line.

    I assume that (a) this is not a good thing, and (b) the copper and galvanized lines should be seperated/insulated from each other?

    On the gas line, there's significant corrosion bloom "bleeding" from the galvanized line to the copper. At what point should I be concerned that the gas line needs replacing?

  2. #2
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    zinc ( the coating on galvanized pipe) act as a sacrificial anode when near a more noble metal ( copper ) . Dampness in the ground provides the electrolyte for this reaction to take place.

  3. #3
    In the Trades Wally Hays's Avatar
    Join Date
    Nov 2009
    New England


    Now is a good point to be concerned. Have the gas company or a gas service tech come out and advise you.
    Perception is 3/4 of reality

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    Galvanized, or black, steel gas pipes should NEVER be direct buried in the ground, regardless of whether they are touching copper lines or not. They require special factory applied coatings and specific installation procedures to be used for underground gas lines. In fact, some cities in this area require "cathodic bags" to be attached to underground metal gas lines to protect against failure, even when the approved materials ARE used.

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