US DOT Hazardous Materials Regulations (49 CFR Parts 171 to 180) 180.405-417: Continuing qualification of cargo tanks: external and internal visual, lining, leakage, pressure and thickness tests at the 180.407 intervals, by Registered Inspectors, with repairs, marking and records (180.401 to 180.417)

A cargo tank motor vehicle may be used for hazardous materials only if it has passed the tests and inspections of 180.407 at the intervals in the 180.407(c) table (external visual inspection annually, internal visual inspection generally every five years with the exceptions for lined and certain tanks, lining inspection annually where applicable, leakage test annually, pressure test every five years for most specifications and more frequently for certain MC 330 and 331 tanks in corrosive service, thickness test every two years for unlined tanks in corrosive service), performed by a Registered Inspector and, for pressure tests on certain tanks, with the procedures and acceptance criteria the section prescribes, and the tank marked with the test type and date (180.415). Repairs, modifications, stretching and rebarrelling must follow 180.413, with the work done by a qualified facility and recertified where required. The owner must keep the test and inspection reports, the manufacturer's certificate and data report, and records of repairs for the periods in 180.417, and the operator must carry or have available the certificate of compliance.