(a) When a premises has an auxiliary water supply which is not or may not be of safe bacteriological or chemical quality and which is not acceptable as an additional source of water by the director, then the city's water system shall be protected against backflow from that premises by installing an approved backflow prevention assembly in the water service connection which is appropriate to counter the degree of hazard.

(b) If a premises is one on which any industrial fluids or any other objectionable substance is handled in a way that creates an actual or potential hazard to the city's water system, then the public water system shall be protected against backflow from that premises by installing an approved backflow prevention assembly in the water service connection which is appropriate to counter the degree of hazard. The term objectionable substances as used herein includes, but is not limited to, process waters and waters originating from the city's water system which have been subjected to a deterioration in quality.

(c) On premises

(a) On any premises where there is an auxiliary water supply as set forth in subsection (1)(a) of this section, the city's water system shall be protected by an approved air-gap separation, an approved reduced pressure principle backflow prevention assembly, or an approved reduced pressure principle-detector assembly.

(b) On any premises where there is water or substance that would be objectionable but not hazardous to health if introduced into the city's water system, the city's water system shall be protected by an approved double check valve assembly, or an approved double check-detector check valve assembly.

(c) On any premises where there is any material dangerous to health which is handled in such a way that creates an actual or potential hazard to the city's water system, the city's water system shall be protected by an approved air-gap separation, an approved reduced pressure principle backflow prevention assembly, or an approved reduced pressure principle-detector assembly. Examples of premises where these conditions exist include sewage treatment plants, sewage pumping stations, chemical manufacturing plants, hospitals, mortuaries, and plating plants.

(d) On any premises where there are “uncontrolled” cross connections, either actual or potential, the city's water system shall be protected by an approved air-gap separation, an approved reduced pressure principle backflow prevention assembly, or an approved reduced pressure principle-detector assembly at the water service connection.

(e) On any premises where, because of security requirements or other prohibitions or restrictions, it is impossible or impractical to make a complete in-plant cross connection survey, the city's water system shall be protected against backflow from that premises by either an approved air-gap separation, an approved reduced pressure principle backflow prevention assembly, or an approved reduced pressure principle-detector assembly on each water service connection to the premises.