A hydration system with an improved fluid reservoir. A drinking tube extends from an outlet port of the reservoir and includes a distal end upon which a mouthpiece may be mounted. In some embodiments, the reservoir includes a relatively large-diameter fill port. In some embodiments, the reservoir includes a closure member with a handle for selectively sealing the input port. In some embodiments, the reservoir includes a wrench assembly that enables the user to more easily open and close the input port and/or to position the reservoir for filling. In some embodiments, the hydration system includes a pack into which the reservoir is received, and in some embodiments, the pack includes a hanger assembly adapted to support the reservoir within the pack.