An apparatus for coupling to a fluid delivery system and for receiving a fluid into the apparatus; a portion of the apparatus permitting a change in shape or size to accommodate the fluid volume or pressure received therein. The apparatus including a housing with a cavity, an expandable reservoir with an opening and a passage, and a cap; the expandable reservoir positioned within the cavity and coupled to a fluid source. The expandable reservoir includes an unrestrained orientation when a fluid volume or pressure therein is below a threshold, and an expanded orientation, when the fluid volume or pressure therein is above the threshold; the expandable reservoir moving toward the expanded orientation to accommodate a fluid volume or pressure received through an opening, and the expandable reservoir moving toward the unrestrained orientation to direct a fluid volume or pressure through an opening.