AIR GAP (AG) SEPARATION: The unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet supplying water to tank, plumbing fixture or other device and the flood level rim of the receptacle, and must be at least double the diameter of the supply pipe measured vertically above the flood level rim of the vessel. In no case may the gap be less than one inch (1").
APPROVED ASSEMBLY: Any backflow prevention assembly which has satisfactorily completed laboratory and field tests by an independent laboratory recognized by the Idaho department of health and welfare and/or the Idaho department of environmental quality, and which is selected by the owner, user or occupant from the state approved list.
AUXILIARY SUPPLY: Any water source or system other than the city water system that may be available in the building or on the premises.
BACKFLOW: The flow, other than the intended direction of flow, of any foreign liquids, gases or substances into the distribution of the public water system.
Back Pressure: Backflow caused by a pump, elevated tank, boiler or other means that could create pressure within the system greater than the potable water supply system.
Back Siphonage: A form of backflow due to a negative or subatmospheric pressure within the water system.
BACKFLOW PREVENTION ASSEMBLY: An assembly to counteract back pressures or prevent back siphonage.
CROSS CONNECTION: Any physical arrangement whereby a public water system is connected, directly or indirectly, with any other nonpotable water system, sewer, drain, conduit, pool, storage reservoir, plumbing fixture or other device which contains, or may contain, contaminated water, sewage or other waste liquid of unknown or unsafe quality which may be capable of imparting contamination to the public water system as a result of backflow. Bypass arrangements, jumper connections, removable sections, swivel or changeover devices, or other temporary or permanent devices through which, or because of which, backflow may occur are considered to be cross connections.
DOUBLE CHECK VALVE ASSEMBLY (DCVA): An assembly composed of two (2) single, independently acting check valves, including resilient seated tightly closing shutoff valves located at each end of the assembly and equipped with properly located resilient seated test cocks for testing the water tightness of each check valve.
PRESSURE VACUUM BREAKER BACK SIPHONAGE PREVENTION ASSEMBLY (PVBA): An assembly containing an independently operating internally loaded check valve and an independently operating internally loaded air inlet valve located on the discharge side of the check valve. The assembly is to be equipped with properly located resilient seated test cocks and tightly closing resilient seated shutoff valves attached at each end of the assembly. This assembly is designed to protect against a back siphonage condition only.
REDUCED PRESSURE PRINCIPLE BACKFLOW PREVENTION ASSEMBLY (RPBA): An assembly incorporating two (2) or more check valves and an automatically operated differential relief valve located between the two (2) checks. Two (2) resilient seated shutoff valves, one located at each end of the assembly and equipped with properly located resilient seated test cocks for testing. The assembly must operate to maintain the pressure in the zone between the two (2) check valves, less than the pressure on the public water system side of the assembly. At cessation of normal flow, the pressure between the check valves must be less than the supply pressure. In case of leakage of either check valve, the differential relief valve must operate to maintain the reduced pressure by discharging to the atmosphere. When the inlet pressure drops below two (2) pounds per square inch, the relief valve must be open to the atmosphere thereby providing an atmospheric zone between the two (2) check valves. (Ord. 452, 1-7-2014)