Abstract: An integral nut and washer formed from a fiber reinforced polymeric material that is particularly useful for use in water tanks and the like that are bolted together from overlapping metal plates. The combination includes a generally cylindrical nut body having an internally threaded cavity, with a transversely extending washer portion around the opening. At least one pair of opposed flats are provided on the nut body for tightening the nut with a conventional wrench. An axial vent is provided at the closed end of the cavity to allow air or excess sealant, where sealant is used, to escape as the nut is tightened. The entrance into the threaded cavity is chamfered, and the washer portion is tapered back along the nut portion for maximum washer strength. Preferably, the integral nut and washer is formed from a glass fiber reinforced polyurethane material by injection molding. This nut is durable and does not corrode in use.