My initial reaction is that it would be a nice audio visual device, but that if the operators, etc. have not learned about them by the time they have gotten their jobs, then they are in the wrong positions. Backflow prevention is so elemental and necessary, that it should be one of the first items a trainee learns. Especially in a water distribution center. And no amount of A/V aids will prevent a worker from installing the proper device improperly, as I once saw in a U.S. Post Office.