A. “Air-gap separation” means the unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet supplying water to a 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.

B. “Auxiliary supply” means any water source or system, other than the public potable water system, that may be available in the building or on the premises.

C. “Backflow” means the reversal of flow, other than in the intended direction, into the distribution of the public water system, from a service connection.

D. “Backflow-prevention device” means an approved device to counteract back pressure or prevent back siphonage.

E. “Cross-connection” means 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 or liquid of unknown or unsafe quality which may be capable of imparting contamination into the public water system as a result of backflow. Bypass arrangements, jumper connections, movable sections, swivel or changeover devices, or other temporary or permanent devices through which, or because of which, backflow could occur, are considered to be cross-connections.

F. “Double check-valve assembly (DCVA)” means an approved assembly composed of two single, independently acting check valves, including tightly closing shutoff valves located at each end of the assembly and suitable connections for testing the watertightness of each check valve.

G. “Reduced-pressure-principle backflow-prevention device (RPBD)” means an approved device incorporating two or more check valves located between the two checks, two shutoff valves, and equipped with the necessary appurtenances for testing. The device must operate to maintain the pressure in the zone between the two check valves, less than the pressure on the public water system side of the device. 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 operation to maintain the reduced pressure by discharging to the atmosphere. When the inlet pressure drops below two pounds per square inch, the relief valve must open to the atmosphere thereby providing an atmospheric zone between the two check valves. (Ord. 88-14 § 4, 1988)