For some postsurgical patients and stroke victims, a drainage bag is used to discharge urine. As a small and intermittent amount of urine drains down the small tube, urine needs to travel around the confined air bubbles that occupy the tube. As the urine squeezes through the gap between the air and the tube’s wall, the air bubbles slowly rise and allow urine to travel downward. The resistance of such film flow is significant and the urine may become stagnant or backflow, resulting in painful pressure on a sensitive part of the body. Bacterial colonization of catheters is common. Each day of catheter use increases the chance for the appearance of bacteria in the urine by 5%. These infections can have serious consequences, including death. Infections can be prevented by maintaining a closed drainage system, keeping high infection control standards and by preventing backflow from the catheter bag. To prevent the backflow from the catheter bag in a closed drainage system will require the improvement of liquid flow through closed tubes in the presence of confined bubbles. This paper demonstrates the use of a tube with a superhydrophobic coating together with either angular cross section, embedded thin fins, or a spiral thread in order to improve the drainage under the aforementioned situations. Due to the superhydrophobic coating, the liquid will tend to stay away from the tube’s surface and because of the angular geometry or other geometric modifications, liquid will not occupy these corner areas. As a result, liquid will tend to move in the central region of the tube while the air counterflow will use the passage near the corners. The outcome was impressive, with bubbles no longer obstructing the flow. Thus, the combination of the effect of modified cross section geometry and the hydrophobic coating will prevent the confined bubble from obstructing liquid flow in tubes. The applications to the improvement of urinary catheters design are discussed in this paper.