AIR GAP. Used to prevent either backflow or backsiphonage, an air-gap separation is 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.
ATMOSPHERIC VACUUM BREAKER (NON-PRESSURE TYPE BACKSIPHONAGE PREVENTER). Used to protect for direct or indirect water connections to all types of polluted or contaminated liquids where the preventer is not subject to back-pressures and is installed on the discharge side of the last control valve. This preventer should not be subjected to continuous flows for periods of more than 12 hours.
BACKFLOW. The flow of water or other liquids, mixtures or substances into the water distribution system from other than the intended liquids, mixtures or substances of the public water supply system.
BACKSIPHONAGE. The flowing back of water or other liquids, mixtures or substances into a water distribution system due to negative pressure in the piping of the water distribution system.
CROSS-CONNECTION. Any actual or potential connection or structural arrangement within a water distribution system through which it is possible to introduce into the public water supply system any water, liquids, mixtures or substances, other than the intended water, liquids, mixtures or substances of the public water supply system.
DOUBLE CHECK-VALVE ASSEMBLY (BACKFLOW PREVENTER). Used as protection for all direct or indirect water connections through which foreign substances might enter the system in such concentrations as to constitute a nuisance or be aesthetically objectionable. Examples are foods, beverages or other substances which do not constitute a health hazard.
NON-TOXIC SUBSTANCE. Any substance of a nonpoisonous nature which may create a moderate or minor hazard to the domestic water system. Hazardous connections include:
(1) Connections to food processing lines, including, but not limited to, those carrying syrups, lard or beer;
(2) Connections to steam and steam boilers where the steam does not come in contact with toxic substances;
(3) McDaniel tees or steam clean-up connections in food plants, apartment house boilers or pressing boilers where toxic compounds are not used; and
(4) Connections to enclosed circulating systems, such as radiant-heating systems and refrigerated-water systems where toxic compounds are not used.
PRESSURE VACUUM BREAKER (BACKSIPHONAGE PREVENTER). Used as a protection for direct or indirect water connections to all types of polluted or contaminated liquids where the preventer is not subjected to backpressure. This device may be installed for use under continuous line pressure.
REDUCED-PRESSURE DE-ICE (BACKFLOW PREVENTER). Used as a protection for direct or indirect water connections where the device may be subject to backpressures from toxic chemicals, sewage or other lethal substances.
TOXIC SUBSTANCE. Any substance (liquid, solid or gaseous), including raw sewage and lethal substances, which, when introduced into the water supply system, creates or may create a danger to the health and well-being of the consumer. Hazardous connections include flush valve toilet, direct connection to contaminated vessel or system, and ship water point.
(1999 Code, § 3-122)