Fire protection systems ARE considered non-potable systems due to the poor quality of water often found in them, and due to chemicals added to minimize corrosion of the sprinkler lines.
Fire protection systems that are connected to the potable water system, either directly or indirectly on the property side of a potable water service, must be isolated with an approved backflow prevention assembly. The level of backflow protection shall be commensurate with the degree of hazard.
The City requires a detector meter on the backflow device to detect any unauthorized use or leakage within the system. Most fire protection systems will have a fire department connection on the fire line. In these cases, the FDC connection must be installed downstream of the backflow prevention assembly.