Abstract: A gate valve has a body having a cavity and a stem passage extending from the cavity. A stem extends through the stem passage into the cavity for moving a gate in response to rotation of the stem. A conical backseat seal surface is formed at a junction of the stem passage with the cavity. A backseat seal has a leg extending outward from the stem and away from the stem passage. The leg has an outer surface with a sealing band that is spaced from the backseat seal surface during normal operation of the valve. The leg is flexible, causing the sealing band to deflect into sealing engagement with the backseat seal surface when the stem is moved axially to a backseat sealing position.