How often should my Luxfer 6351-alloy scuba tank be inspected? DOT requires requalification (hydrostatic retesting and visual inspection) of all aluminum scuba tanks every five years, regardless of alloy. Both the DOT and the U.S. scuba industry recommend an annual visual inspection for all 6351-alloy scuba tanks. Luxfer supports this recommendation. For its 6351-alloy tanks, Luxfer has established a manufacturer's requirement for a visual inspection, including an eddy-current test, at least every 2.5 years.