If you see CO2 leaking from disconnected quarter-inch tubing, it tells you what?

• A. The quarter-inch tubing is defective
• B. The system is over-pressurized
• C. That your check valve has failed
• D. Leakage indicates a faulty regulator

Answer: (C)

In a CO2 system, a check valve keeps gas from flowing backward into the supply and helps isolate sections when a line is disconnected. If CO2 is leaking from a disconnected quarter-inch tube, gas is being pushed past that valve into the now-open line. That means the check valve isn’t sealing properly and has failed. The other parts would show different symptoms: leaking tubing would show gas along the hose itself, an over-pressurized system would push gas out at fittings or the regulator, and a faulty regulator would leak at the regulator or cause abnormal pressure, not specifically indicate backflow past a failed check valve.