An air admittance vent diaphragm assembly is disclosed. The assembly comprises a base, an annular retainer ring, and an annular malleable washer. The base has an annular portion and a stem extending orthogonally from the center of the annular portion. The annular retainer ring includes a circumferential skirt engaged with an outer perimeter of the annular portion of the base, with the stem extending beyond the annular retainer ring. The annular malleable washer is disposed between the annular retainer ring and the annular portion of the base.