When pressure testing a completed copper tubing assembly with pressurized nitrogen cylinders, this should ______.

• A. Be performed only for non-reactive metals
• B. Be done outdoors only
• C. Always be used with a regulator
• D. Use oxygen instead for testing

Answer: (C)

Controlling gas pressure with a regulator is essential when pressure testing a copper tubing assembly with pressurized gas. The regulator lowers the cylinder’s high pressure to a safe, controllable test pressure and provides a gauge to monitor how much pressure is actually applied. This prevents sudden surges or over-pressurization that could cause leaks, bursts, or dangerous releases. Nitrogen is used because it’s inert and non-reactive, reducing fire or chemical risks during the test, whereas using oxygen would create serious safety hazards. The regulator also helps keep the test within the system’s design limits, making leaks or weak joints detectable without risking an uncontrolled blow-off.