A system for controlling rain water flow includes a container having a top end and an opposite bottom end. A drain tube having a drain port is connected to the container. A cover tube slidably receives the drain tube. A magnetic latch is disposed between the drain tube and the cover tube. The system includes a fill configuration in which the magnetic latch is magnetically engaged and the cover tube covers and seals the drain port of the drain tube. The system also includes a drain configuration in which the magnetic latch is magnetically disengaged and the drain tube slides downward to expose the drain port.