A fluid shut off valve for use in a parenteral fluid administration set includes a disk floating in a fluid chamber that shuts off fluid flow when the fluid in the chamber decreases below a certain level. The chamber includes a valve stem at its lower end that has both a valve seat and an alignment member with an alignment surface on the top end thereof for guiding the disk into proper seating on the valve seat. The valve seat and floating disk have complementary engagement surfaces for also guiding the disk into proper seating on the valve seat. In one embodiment, the alignment member includes fins located both on the valve stem and on the inside wall of the chamber. Because of the configuration of the alignment member, dislodgement of the disk from the valve seat is made easier.