A gas appliance connector that has been reused from a prior installation is a concern because:

Gas appliance connectors seal at their flare fittings through metal-to-metal contact, and that seal is formed by deforming the flare as the nut is tightened. The deformation is plastic, not elastic — the metal takes a permanent set matched to the mating surface it was tightened against. Disconnecting and reinstalling the connector, particularly onto a different fitting, asks a surface that has already yielded to seal again against different geometry, and it frequently does not. The result is a slow leak at a joint that looks correctly assembled and passes a casual glance. That is why connectors are listed for single use, and why an inspector who sees evidence of reuse reports it even when no leak is detectable at the time.

Connectors are listed for a single installation because the flare seal takes a permanent set when first tightened. Reusing one asks that deformed surface to seal again, which it may not do, so a reused connector is a leak risk and is reported for replacement.

Flexible gas connectors are listed for one installation. Manufacturers and fuel gas provisions direct that a connector be replaced rather than reused when an appliance is disconnected, and that connectors not be joined, extended or concealed.

One Flare, One Life. The metal remembers the first joint it was tightened onto and will not honestly seal a second.

Absence of a detected leak does not clear a reused connector. The exam is testing the listing rule, not the result of a soap test on the day.

• •Clearing a reused connector because no leak was detected
• •Confusing the single-use rule with the prohibition on extending connectors
• •Framing a gas safety issue as a warranty matter