Bureau of Operations - Drinking Water
Cross-Connection and Backflow Prevention
Educational Information and References

Please refer to the following links for additional information on cross-connection control and backflow prevention.

American Backflow Prevention Association
http://abpa.org/

Georgia Association of Water Professionals
http://www.gawp.org/

US Environmental Protection Agency, Cross-Connection Control Manual
http://www.epa.gov/safewater/crossconnectioncontrol/index.html

Definitions of commonly used terms:

Air Gap: Backflow prevention characterized by a physical separation between the free flowing discharge end of a Potable Water supply pipeline and an open or non-pressure receiving vessel. The physical separation shall be at least twice the diameter of the supply pipe measured vertically above the overflow rim of the vessel but in no case less than one (1) inch. This configuration can be used to eliminate a Cross-Connection.

Auxiliary Water Supply System: A pressurized or pumping-ready water supply system other than a Public Potable Water System which is located on or available to the Consumer’s property whether or not connected to a distribution system within the property. Such auxiliary systems include but are not limited to Reclaimed Water systems, private water systems and private wells.

Backflow: The undesirable reversal of flow of water or mixtures of waters and other liquids, gases or other substances into the distribution pipes of the potable supply of water from any source(s).

Backflow Prevention Assembly: A mechanical assembly which is supplied with properly located resilient-seated shut-off valves at each end of the Assembly and properly located test cocks, meets the latest standards of the University of Southern California's Foundation for Cross-Connection Control and Hydraulic Research (U.S.C.), American Society of Sanitary Engineers (ASSE), Underwriters Laboratory (UL), and complies with the standard listed in the State Plumbing Code as adopted by the City of Atlanta, and approved by the City of Atlanta Department of Watershed Management.

Backflow Prevention Device: A non-testable unit consisting of a mechanical device or plumbing configuration that is designed for use to prevent Backflow.

Containment: Containment shall mean isolation of a residence or commercial facility from the public water supply system by the installation of a backflow prevention assembly/device commensurate with the degree of hazard, installed on each service line to the customers at or near the property line or immediately inside the building being serviced; but in all cases, before the first branch line leading off the service line.

Cross-Connection: Any unprotected actual or potential connection or structural arrangement between a Public or a Consumer’s Potable Water System and any other source or system through which it is possible to introduce into any part of the Potable Water System any used water, industrial fluid, gas, or substance other than the intended Potable Water with which the system is supplied. By-pass arrangements, jumper connections, removable sections, swivel or changeover assemblies, or any other temporary or permanent connecting arrangements through which, or because of which, backflow can or may occur, are considered to be Cross-Connections.

Double Check Valve Assembly: An assembly composed of two independently acting, approved check valves, including tightly closing resilient-seated shutoff valves located at each end of the assembly and fitting with properly located resilient-seated test cocks. This assembly shall only be used to protect against a non-health hazard.

Hazard: A Cross-Connection or potential Cross-Connection which involves an actual or potential threat to the quality and/or potability of the water supplied by a Public Potable Water System. The degree of Hazard associated with any Private Water System shall be determined from an evaluation of the conditions existing within that system.

Health Hazard: A Hazard involving any substance that could, if introduced into the Public Potable Water System, cause death or illness, spread disease, or have a high probability of causing such effects.

Non-Health Hazard: A Hazard involving any substance that generally would not be a Health Hazard but would, if introduced into the Public Potable Water System, constitute a nuisance, be aesthetically objectionable and/or cause minor damage to the system.

Non-Potable Water: Water which is unsuitable for human consumption or which is of questionable potability.

Potable Water: Water that is suitable for human consumption.

Potable Water System: All facilities utilized for the production, treatment, storage, transmission, distribution and delivery of Potable Water within the City and County.

Public Potable Water System: A Potable Water System as defined by the State of Georgia EPD.

Reduced-Pressure Principle Assembly: A Backflow Prevention Assembly which includes two independently acting check valves; a hydraulically operating, mechanically independent pressure differential relief valve located both between the check valves and below the first check valve; and properly located test cocks and tightly closing resilient-seated shut-off valves attached at each end of the Assembly. This assembly is primarily used to protect against High Hazzards.

Thermal Expansion: A common occurrence in which the volume of water increases when it is heated. When a piping system is protected with a Backflow Prevention Assembly, thermal expansion can increase the water pressure within the closed piping system. In order to control the increased water pressure due to thermal expansion, plumbing codes require the installation of a surge tank. Click here for additional information.

Water Service Connection: The point of connection to the Public Potable Water System (metered or non-metered) where the Utility loses jurisdiction and sanitary control over the Potable Water delivered to that point. Included within this definition are connections for fire hydrants and other temporary or emergency water service. For metered connections, the point of connection is just downstream of the water meter box, vault or slab, as shown on City of Atlanta Department of Watershed Management, Bureau of Drinking Water standard details. This is also referred to as the point of delivery.