Down the tubes is an idiom that is used to describe something that has failed or gone wrong. It can be used to describe a situation, a plan, or an idea. In this context, the crossword solutions BAD (3 letters), KAPUT (5 letters), and SHOT (4 letters) all refer to something that has gone wrong and has been ruined. BAD implies something that is not good or of poor quality, KAPUT means completely destroyed or ruined, and SHOT implies something that has been ruined beyond repair. Together, these words paint a picture of something that has gone wrong and has been ruined beyond repair.