A tank-tube viscometer and its novel non-Newtonian viscosity equation were developed to determine flow characteristics of non-Newtonian fluids. The objective of this study is to test capabilities of the tank-tube viscometer and its novel non-Newtonian viscosity equation by characterizing rheological behaviors of dairy products. The rheological behavior of fluid milk such as simulated fluid milk and grocery fluid milk such as skim milk and whole milk were characterized with the viscometer, using water as a reference calibration fluid. The non-Newtonian viscosity equation was developed under the assumptions that a quasi-steady state approach is valid, and the friction loss due to a sudden contraction between the reservoir tank and the tube is negligible for laminar fluid flows, using L'Hospital's rule. Simulated fluid milk was prepared by adding dry nonfat milk powder to water, whereas commercial fluid milk such as skim milk and whole milk was purchased from a grocery store. The only experimental data required is the mass of the fluid milk that drains from the viscometer at a given drain duration. The concentration of dry nonfat milk powder in simulated fluid milk ranges from 4 to 10 wt %. As the concentration of dry nonfat milk powder in simulated fluid milk increases, the flow behavior index of simulated fluid milk decreases. Raising the temperature from 12 to 26 degrees C, the now behavior index of simulated fluid milk containing 4 wt % dry milk powder increases from about 0.7 to 0.9. The apparent viscosity values of the 4 wt % simulated fluid milk exhibits Arrhenius behavior with respect to temperature.