Abstract: A toilet tank valve having a vertical riser with a collet thread and a plurality of flexible collet fingers. A slider tube is fitted into the riser. It has a plurality of peripheral grooves that can be engaged by the fingers to adjust the elevation of the slider tube. A collet nut threaded to the riser compresses the finger for this purpose. Valve workings are mounted to the slider tube. They include an inverted cup float slidingly fitted around the riser which can engage splines on the collet nut so that rotating the float can turn the collet nut, enabling the slider tube's elevation to be adjusted and its adjustment retained.