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Question

Difficulty: MediumPlumbing and Pipe Materials

When connecting a newly installed copper pipe to an existing galvanized steel water supply line, which specialized fitting must be used to prevent rapid electrochemical corrosion between the two dissimilar metals?

  1. Dielectric unionAnswer
  2. B
    Standard threaded steel coupling
  3. C
    Compression reducer bushing
  4. D
    Schedule 40 PVC slip coupling

Answer

Dielectric union
A dielectric union is specifically engineered with an insulating rubber washer and plastic sleeve to isolate copper from galvanized steel, preventing galvanic corrosion in plumbing water supply systems.

Step-by-Step Solution

1
Identify the piping materials involved in the connection
Copper and galvanized steel are two dissimilar metals with different electrical potentials.
Direct contact between copper and steel in the presence of an electrolyte such as water creates a galvanic cell, rapidly corroding the more active metal (steel).
2
Select the appropriate fitting that prevents electrochemical reaction
A dielectric union provides mechanical coupling while incorporating a non-conductive plastic bushing and elastomer washer.
The non-conductive barrier breaks electrical conductivity between the metals, stopping galvanic corrosion.

Key Concept

Galvanic corrosion prevention in dissimilar metal piping systems
Estimated Time:1m 0s
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Topics

Plumbing and Pipe Materials

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