Apparatus and method for determining endpoint of a fluid supply vessel in which fluid flow is controlled through a flow passage disposed in an interior volume of the fluid supply vessel with a static flow restricting device and a selectively actuatable valve element upon establishing fluid flow. The endpoint determination can be employed to terminate fluid supply from the fluid supply vessel and/or to switch from a fluid-depleted supply vessel to a fresh vessel for continuity or renewal of fluid supply operation. The apparatus and method are suitable for use with fluidutilizing apparatus such as ion implanters.