A water reservoir for an apparatus for humidifying a flow of air for delivery to an entrance of the airways of a patient for respiratory therapy includes a reservoir base configured to hold a volume of water, a reservoir lid comprising an inlet and an outlet, a hinge joint to pivotally couple the reservoir lid to the reservoir base for pivotal movement between an open position and a closed position, wherein the reservoir lid and the reservoir base cooperate to form a sealed internal volume at the closed position, and a rotation stop, wherein the rotation stop is arranged between the reservoir lid and the reservoir base at the open position, and wherein the rotation stop is configured and arranged to disconnect the reservoir lid from the reservoir base at the hinge joint when the reservoir lid is over-pivoted beyond the open position.