In a chilled water system, a connection between different metallic piping materials must be made with ____________.

• A. Dielectric fittings
• B. Copper couplings
• C. Flanged joints
• D. Soldered joints

Answer: (A)

Connecting different metallic piping materials in a chilled water system must provide electrical isolation between the metals to prevent galvanic corrosion. Dielectric fittings accomplish this by placing insulating materials between the different metals, so the water cannot carry electrical current directly between them. This keeps the more anodic metal from corroding and prevents leaks that result from accelerated corrosion over time. Without isolation, a copper-to-steel or cast iron-to-copper joint would set up a galvanic couple in the presence of the circulating water electrolyte, leading to premature failure. Dielectric fittings are specifically designed for this purpose and are common wherever two different metals must be joined in HVAC piping. Other joining methods like copper couplings, soldered joints, or standard flanged joints create or maintain a conductive metal path between dissimilar metals, so they are not appropriate for preventing galvanic corrosion in this scenario.