Abstract: Nearly all residential and commercial buildings in the United States contain systems for the collection, flow, and run off of rainwater and condensation. Most of that water is funneled into existing municipal drainage systems or simply diverted onto the adjoining ground, but away from the building structure. This invention adds to that system a means to capture and store some of that water. It is intended primarily for residential use, but could be used in commercial applications as well. The invention interrupts the flow of water traveling through the down spout and diverts a preset amount into a storage tank. An exit back into the existing down spout carries all water back into the drainage system over and above that stored in the tank. It contains a flow control system that can be set to force all water through the normal drainage system, this is primarily for cold weather climates where freezing would be a concern in the storage tank.