Truck and trailer containers shall be equipped with a liquid level gauging device of approved design, such as a fixed tube device. Fixed tube devices shall be arranged so that the maximum liquid level to which the container may be filled is set at the maximum permitted for the container based on an initial liquid temperature not to exceed 40 degrees Fahrenheit. An isolation valve shall be installed between the container and the liquid level gauging device.
16 Tex. Admin. Code § 14.2722