Section 19.183 - Scale tanks(a) Except as otherwise provided in paragraph (b) of this section, if the proprietor uses a tank to determine the distilled spirits tax imposed by 26 U.S.C. 5001 , the tank must be mounted on scales and the contents of the tank must be determined by weight. The scale tank also must be equipped with a suitable device so that the volume of the contents can be quickly and accurately determined.(b) The requirement to mount tanks on scales does not apply to tanks having a capacity of 55 gallons or less. Such tanks may be moved onto an accurately calibrated scale when a tax determination gauge needs to be made.26 U.S.C. 5006 , 5204 , 5505