[Code of Federal Regulations] [Title 46, Volume 2] [Revised as of October 1, 2004] From the U.S. Government Printing Office via GPO Access [CITE: 46CFR64.19] [Page 319] TITLE 46--SHIPPING CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PART 64_MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS--Table of Contents Subpart B_Standards for an MPT Sec. 64.19 External pressure. (a) A tank without a vacuum breaker must be designed to withstand an external pressure of 7\1/2\ psig or more. (b) A tank with a vacuum breaker must be designed to withstand an external pressure of 3 psig or more.