The production and delivery of safe water is the highest priority for a public water supply system. After potable water has been produced, precautions must be taken to ensure that it is not contaminated with water, liquids, gases, or corrosion products from other sources.
Almost every water user in the distribution system may have actual or potential hazards. Simply misusing an ordinary garden hose may create a potentially dangerous cross-connection. Private water users may have complex internal water systems, such as would exist at hospitals, large buildings, industrial plants, and food processing facilities. Contaminated backflow into the public water system occurs either through back pressure or back siphonage, from appliances and equipment, or from other water supply sources.
Customer & Purveyor Responsibilities
The water user (customer) has a responsibility to protect the safety of the water supply - both on their premises and in the public system. Protection of building plumbing must be done in accordance with the requirements of the adopted plumbing code and local authority having jurisdiction.
Clearly, the water purveyor has the responsibility to protect the public water supply for all of its customers. Therefore, cross-connection control programs generally require backflow prevention assemblies within private water systems as well as backflow prevention devices installed at water service connections. Such duplicate protection devices help to ensure the integrity of the public water system.