Where should a dielectric union be located in the system?

Where should a dielectric union be located in the system?

• A. Between regulator and indoor piping
• B. Between riser and indoor piping
• C. Between tank and regulator
• D. Between service entrance

Answer: (B)

Dielectric unions prevent galvanic corrosion by electrically isolating two different metals in a gas piping system. When outdoor piping (typically steel) connects to indoor piping (often copper), moisture or soil contaminants can create an electrochemical cell that corrodes the metal at the joint. Placing a dielectric union at the transition between the riser and the indoor piping stops electrical current between the dissimilar metals, protecting the interior copper run from corrosion and leaks. The junction between the tank and regulator or other exterior points doesn’t address this mineral-metal interaction in the same way, and the service entrance isn’t part of the gas piping transition.

Dielectric unions prevent galvanic corrosion by electrically isolating two different metals in a gas piping system. When outdoor piping (typically steel) connects to indoor piping (often copper), moisture or soil contaminants can create an electrochemical cell that corrodes the metal at the joint. Placing a dielectric union at the transition between the riser and the indoor piping stops electrical current between the dissimilar metals, protecting the interior copper run from corrosion and leaks. The junction between the tank and regulator or other exterior points doesn’t address this mineral-metal interaction in the same way, and the service entrance isn’t part of the gas piping transition.