with the green basics automatic filling device for rain barrels you can easily connect your rain barrel to a downpipe, the rain barrel fills automatically during a rain shower, when the barrel is full, the excess water flows down the drain, the automatic filling device is suitable for the most common downpipe sizes, for 70, 80 and 100 mm diameter and a square version, use the fitting that matches your downpipe and use the automatic filling device for rain barrels from green basics in combination with your rain barrel and your downpipe