I recently noticed that one of the ducts came loose from air handler in the attic. It seems that duct tape was all that was holding it there. There's about an inch of collar sticking out (6.5" diameter), and I'm unable to reconnect duct back to it, cause it's soft and keeps slipping off. Is there some kind of adapter I can buy at hardware store to make connection? Duct itself seems to be about 7" diameter, does that sound right?