A hydrostatic test must be performed every five years. During this test the cylinder is overfilled to a specified amount and its permanent expansion is measured. If the cylinder meets passing criteria the test date is permanently stamped on the cylinder
Visual inspections must be performed on an annual basis. During this test the inside and outside of the cylinder is inspected for signs of cracks, pits, rust, or corrosion. The test date is marked on a sticker that is placed on the tank as evidence of the inspection.