During my time in the Navy I was a Machinist's Mate, which encompasses many skills including many things a plumber does. Although I was a nuclear propulsion plant operator I still had to go through training on repairing pumps, valves, piping, etc. I understand these cruise ship problems and know how and why they happen. I also understand when the crew simply can't do anything about it without taking an entire system offline for hours or even days in order to effect repairs or a remedy. Passengers will not often understand why, but they do deserve a polite and complete explanation by the management.