In-Plant Isolation

If the public water system only employs the uses the containment principle to protect the public water supply from backflow and ignores the cross-connection hazards within the building, the public water system may be guilty of negligence, if a cross-connection incident occurred within the facility and caused harm.

Domestic internal water system cross-connection protection protects the public water system and all consumers of water. Testable and non-testable devices are utilized to control the cross-connection pursuant to the plumbing code requirements. Domestic internal water system cross-connection protection requires cross-connection survey work of the domestic water supply to the point of use or last free flowing outlet and the installation of backflow prevention device at each outlet or connection to a fixture or non-potable system. This approach to cross-connection control and backflow prevention is much more effective in the protection of the public health than containment protection alone, since all cross-connection are control where they exists utilizing fixture outlet protection and internal protection.

Based on the degree of hazard assessment, the public water system shall take appropriate actions to control the cross-connection. The type of backflow prevention device required at the water meter or at an individual fixture is determined by the evaluating the degree of hazard of the cross-connection. The degree of hazard is based on the existence of the connection between the potable and non-potable water, the probable for backflow to occur and the impact on the quality of water if backflow were to occur. Based upon this evaluation of the cross-connection, the appropriate backflow prevention device shall be installed to control the cross-connection.