Hydrostatic testing is an approved way to test the structural integrity of a cylinder. By law, refrigerant recovery cylinders must be hydro tested and recertified every five years. Our Hydro Test procedure consists of removing the cylinder valve(s), inspecting the cylinder externally and internally, filling the cylinder with water and then pressure testing the cylinder to the approved pressure. If the cylinder passes it's expansion parameters, the cylinder is emptied of water and dried. The cylinder is then stamped with our DOT registration number and test date if it passes. Our Hydro Equipment meets the US DOT requirements for accuracy & readability.