Abstract: A downspout baffle mechanism is disclosed, adapted for use in conventional, vertically disposed downspouts for diverting controlled amounts of water descending in such downspouts to water collecting means located above and spaced from the normal downspout terminus. The baffle mechanism is controlled by the rise and fall of a suitable float in the water collecting means through a motion reversing mechanism such that the baffle diverts water through a side opening in the down position of the float and substantially seals such side opening in the up position of the float. The baffle and control mechanism is preferably incorporated in a preformed assemblage adapted for insertion in a conventional downspout by merely removing, at the desired elevation, an appropriate length of the downspout.