couldn't run a bath

Couldn't manage or direct someone or something. The phrase puns on the word "run," which means both to manage a place or group and, in the context of a bath, filling the bathtub with water. Why in the world did they promote David to manager? That guy couldn't run a bath! A: "Did you hear that Sam got promoted to General Manager?" B: "You've got to be kidding me! That guy couldn't run a bath!" A: "Our elected officials haven't gotten anything major accomplished." B: "Oh, those fools couldn't run a bath. I've lost all faith in them."