CFR › Title 46 › Part 64 › §64.1946 CFR §64.19Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗Copy link(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.