(a) Gauging equipment and methods. A proprietor of an alcohol fuel plant must perform periodic gauges of the distilled spirits and fuel alcohol at the alcohol fuel plant. The procedures for the gauging of spirits set forth in part 30 of this chapter also apply under this subpart. In addition, the following rules for the gauging of distilled spirits and fuel alcohol under this subpart also apply:

1. (1) The proprietor must determine the proof of spirits by using a glass cylinder, hydrometer and thermometer;
2. (2) The proprietor must ensure that hydrometers, thermometers, and other equipment used to determine proof, volume, or weight are accurate;
3. (3) The proprietor may determine the quantity of spirits or fuel alcohol either by volume or weight;
4. (4) To determine quantity by volume, the proprietor may use a tank or receptacle with a calibrated sight glass installed, a calibrated dipstick, conversion charts, an accurate mass flow meter, or other devices approved by the appropriate TTB officer;
5. (5) Unless the proprietor chooses to do so, the proprietor is not required to determine the proof of fuel alcohol manufactured, on hand, or removed; and
6. (6) The proprietor may account for fuel alcohol in wine gallons;

(c) When gauges are required. A proprietor must gauge spirits and record the results in the records required by § 19.718, at the following times:

1. (1) Upon completing the production of distilled spirits;
2. (2) On the receipt of spirits at the plant;
3. (3) Prior to the addition of materials to render the spirits unfit for beverage use;
4. (4) Before withdrawal from plant premises or other disposition of spirits (including fuel alcohol); and

5. (5) When spirits are inventoried.

   (26 U.S.C. 5201, 5204)