Trumpet Vine. I wouldn't recommend it to grow up a downspout. I had one growing on a PVC trellis and had to dig it out after 4-5 years due to it pushing/moving the trellis . This is a very strong woody vine that could probably pull your downspout off the house. Also the seeds do sprout lots of new babies and roots travel. Try researching an annual vine. TV doesn't like any attention so if it hasn't bloomed don't fertilize or water.
Zone 8 gardener.
