Cylinders and tanks must be hydrostatically retested according to regulations at what minimum interval?

The correct answer is that cylinders and tanks must be hydrostatically retested at a minimum interval of every 5 years. This requirement is in place to ensure the integrity and safety of these containers, which are critical in preventing leaks and failures that could lead to dangerous situations, especially in emergency services like firefighting.

Hydrostatic testing involves filling the cylinder or tank with water and applying high pressure to check for any leaks or weaknesses in the material. This not only assesses the physical condition but also ensures that the devices will perform as expected under operational pressures.

While visual inspections are a necessary part of regular maintenance and can help identify obvious signs of wear or damage, they do not replace the need for thorough hydrostatic testing. The less frequent intervals, such as once a year or every six months, do not meet the rigorous safety standards established by regulations for the testing of pressurized cylinders and tanks.