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dielectric union from stainless steel to galvanized pipe

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  • dielectric union from stainless steel to galvanized pipe

    Anyone ever had to use a dielectric union for stainless steel to galvanized pipe? By the way it is on an air line, not water.

  • #2
    Re: dielectric union from stainless steel to galvanized pipe

    u could save yourself the cash by just putting a brass adapter or valve.
    hot on the left, cold on the right... so hot ladies to the left and cold drinks to the right? lets hope gravity keeps em down all night!

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    • #3
      Re: dielectric union from stainless steel to galvanized pipe

      Not a plumber but have an extensive background in corrosion control. The steel (i.e. galvanized exterior) pipe will corrode on the inside where there is water or foam agent (much worse with foam agent). The SS is cathodic to the steel, meaning the steel will corrode to protect the SS. Most of the corrosion will be close to the joint if a dielectric is not used (probably in the threads of the galvanized pipe.). The rate of the corrosion will be based on the amount of stainless exposed to the electrolyte (i.e water or other agent inside the pipes) compared to the amount of steel. Brass will also cause the same failure, but not as quickly.

      If it is a dry system, its a waste of money IMHO but you have to follow local codes and/or contract specs. If the union is wet internally, than a dielectric is called for. Make sure you do not over-tighten and crack the dielectric sleeve.

      Yes, brass bibs are used on galvanized pipe in much plumbing, but in a fire system, lives are depending on it so it is held to a higher longevity standard.

      Go
      Last edited by Gofor; 03-18-2009, 08:05 PM.
      Practicing at practical wood working

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