A water management system for a double hung window prevents leakage between the lower sash and the frame of the window in a blowing rainstorm. The water management system comprises interior pressure-drop seals disposed between the vertical stiles of the lower sash and the jambs of the window frame and an interior pressure drop seal disposed along an interior edge of the bottom rail of the lower sash and the sill of the frame. Exterior shingling seals are disposed at least between outside edges of the sash and the jamb and the exterior shingling seals and the interior pressure-drop seals at least partially bound vertical channels. A vent communicates between the vertical channels and the outside environment to maintain the pressure in the vertical channels substantially the same as that of the outside environment. This prevents rainwater in a blowing rainstorm from violently breaching the exterior shingling seals and splashing onto the interior pressure-drop seals, which, in turn, prevents leaks into a home.