A drain system is disclosed for use with aluminum screen enclosures to allow for adequate drainage of surface water accumulating on the deck. A screen enclosure base rail is adapted with at least one section having a one-way drain apparatus through which water and debris may flow. A pivotal door disposed within the drain apparatus functions as a one-way door to allow water to drain from the enclosed area while preventing water and/or animals from entering. The drain system is preferably incorporated into an otherwise conventional screen enclosure base rail at one or more suitable locations to provide adequate drainage, and does not adversely effect installation of the screen enclosure, nor does it effect structural integrity.