After using the downspout-extension system for a couple of years, I realized that there is a better way to connect the sections, by simply cutting the output of each section as shown in the attached photo, and stuffing it into the input of next section, without cutting the input. By making the cuts longer, the output can be stuffed farther into the input of the next section, which should reduce any leakage without requiring any tape to seal the junction. It's still necessary to tape-up the connection between the "accordion"-adapter and the input of the first section, and for that, I recommend Gorilla tape.
