To provide proper sanitary protection to the corporation's water supply and to comply with the applicable regulations of the United States Public Health Service, the state department of health, and the appropriate county, as adopted or amended from time to time, no cross-connections with other water supplies or other physical connections shall exist or be installed, located, maintained, or operated that could permit backflow of contaminated water or any other dangerous, impure, unsanitary, or unpotable substance from the consumer's premises into the corporation's system.
Haw. Code R. § 15-319-57