One of the major concerns in plumbing is how much protection of potable water is enough? This seems to have become more prevalent with the increasing demand by water utilities to require a backflow preventer on the inlet water supply to a building. This backflow preventer is known as the point-of-supply backflow preventer. Point of supply means it is intended to protect the water supply, not the water in the building.
The first thing you should question is why you need a point-of-supply backflow preventer? Your immediate answer should be you don’t need one. That is the premise of every model plumbing code in this country.