Abstract: A filter dehydrator for sensing the presence of and separating free water in a transient flow of fluid is disclosed comprising an inlet for the fluid, and outlet for the fluid, a mass of water absorptive cellulosic fibers disposed between the inlet and the outlet and a filter medium means upstream of the absorptive mass for removing solid particles that would block the active surface of the mass and for dispersing water droplets in the fluid. The preferred water absorptive cellulosic fiber mass is a water-insoluble cross-linked carboxymethyl cellulose fiber and the preferred filter and disperser is a fiberglass medium filter.