StacksVerified U.S. regulatory reference

49 CFR §179.200-21

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
  1. (a)All plugs shall be solid, with NPT threads, and shall be of a length which will screw at least 6 threads inside the face of fitting or tank. Plugs, when inserted from the outside of tank heads, shall have the letter “S” at least 3/8 inch in size stamped with steel stamp or cast on the outside surface to indicate the plug is solid.
  2. (b)[Reserved]