A single drain mast seal that provides a fluidly segregated internal chamber for air inlet drain lines is provided. The provided drain mast seal does not significantly add to the seal's compressive load and minimizes the seal's three-dimensional space claim. In addition, the provided drain mast seal is formed to sufficiently support associated drain lines without requiring external clamps or hardware components. The provided drain mast seal thereby optimizes the APU-to-drain mast interface.