Abstract: A drain valve has a hollow body threaded to be screwed into a sump drain hole. A stem longer than the body is slidable and rotatable therein, and a washer encircles the stem adjacent the end facing into the sump. A longitudinal channel extends along the stem from its second end to an opening adjacent the washer, and a flange attaches the stem to a wall that covers a groove that extends longitudinally along the outer surface of the valve body, except for a portion offset laterally at the end of the groove closest to the threaded end of the body. A ball is captured between the groove and a recess in the surface of the wall facing the groove. The valve is normally held closed by a spring that forces the stem to slide longitudinally away from the interior of the sump to draw the washer against the body, thereby sealing the stem to the body. To open the valve, the stem is forced longitudinally along the body in opposition to the spring pressure to bring the channel opening within the sump.