Controlling fluid levels in cone-shaped discharge tanks can be challenging, especially in the chemical industry. This paper presents a novel approach for achieving precise level control in such tanks using a proportional-integral (PI) control algorithm. Our method relies on a mathematical model of three interacting conical tanks arranged in a single-input, single-output (SISO) system. By implementing this algorithm, operators can effortlessly maintain the desired fluid level in all three tanks, as specified by the set point. This translates to direct and practical application of the derived controller parameters in real-time process control. The key to our approach lies in a gain scheduling algorithm, developed by analyzing the mass balance equation in the form of differential equations. We provide a detailed step-by-step derivation to guide researchers in their own controller design endeavors. The obtained PI controller values are tested in MATLAB and results are presented.