Protection of the system is required as set forth in the following subsections:
A. 
Auxiliary water supply. Each service connection from a public water system for supplying water to premises having an auxiliary water supply shall be protected against backflow of water from the premises into the public water system, unless the auxiliary water supply is approved as an additional source by the water purveyor and is satisfactory to the public health agency having jurisdiction with regard to quality and safety.
B. 
Substance under pressure. Each service connection from a public water system for supplying water to the premises, on which any substance is handled under pressure in such fashion as to permit entry into the water system, shall be protected against backflow of the water from the premises into the public system. This shall include the handling of process waters and waters originating from the public water supply system which may have been subject to deterioration in sanitary or chemical quality.
C. 
Substance of unusual toxic concentration. Each service connection from a public water system for supplying water to premises on which a substance of unusual toxic concentration or danger to health is handled in liquid form, even though it is not under pressure, shall be protected against backflow of the water from premises into the public system. Examples are plating factories using cyanide and hospitals. This is not intended to apply to normal household installations.
D. 
Internal cross-connections.
(1) 
Backflow prevention devices shall be installed on the service connection to any premises that have internal cross-connections, unless such cross-connections are abated to the satisfaction of the water purveyor.
(2) 
It shall be the responsibility of the water user to provide and maintain these protective devices, and each one must be of a type acceptable to the State Health Department.
The protective device required shall depend on the degree of hazard as tabulated below:
A. 
Double check valve assembly. At the service connection to any premises where there is an auxiliary water supply handled in a separate piping system with no cross-connection, the public water supply shall be protected by an approved double check valve assembly.
B. 
Air-gap separation. At the service connection on any premises on which there is an auxiliary water supply where cross-connections are known to exist or where it is unknown if cross-connections exist, the public water supply system shall be protected by an air-gap separation or an approved reduced-pressure-principle backflow prevention device.
C. 
Objectionable substances. At the service connection to any premises on which a substance that would be objectionable (but not hazardous to health if introduced into the water supply) is handled so as to constitute a cross-connection, the public water supply shall be protected by an approved double check valve assembly.
D. 
Unusual toxic concentration. At the service connection to any premises on which a substance of unusual toxic concentration or danger to health is or may be handled, but not under pressure, the public water supply shall be protected by an air-gap separation or an approved reduced-pressure-principle backflow prevention device. This device shall be located as close as practicable to the water meter, and all piping between the water meter and receiving tanks shall be entirely visible.
E. 
Substance under pressure. At the service connection to any premises on which any material dangerous to health or toxic substance in toxic concentration is or may be handled under pressure, the public water supply shall be protected by an air-gap separation. The air gap shall be located as close as practicable to the water meter, and all piping between the water and receiving tanks shall be entirely visible. If these conditions cannot reasonably be met, the public water supply shall be protected with an approved reduced-pressure-principle backflow prevention device, provided that the alternative is acceptable to the water purveyor.
F. 
Sewage treatment plant or pumping station. At the service connection to any sewage treatment plant or sewage pumping station, the public water supply shall be protected by an air-gap separation. The air gap shall be located as close as practicable to the water meter, and all piping between the water meter and receiving tanks shall be entirely visible. If these conditions cannot be reasonably met, the public water supply shall be protected with an approved reduced-pressure-principle backflow prevention device.
G. 
Other service connections. At the service connection to any premises not covered by Subsections A through F above, the public water supply shall be protected with an approved single check valve assembly.
A. 
It shall be the duty of the water user or any premises on account of which backflow protective devices are installed to have competent inspections made at least once a year or more often in those instances where successive inspections indicate repeated failure. These devices shall be repaired, overhauled or replaced at the expense of the water user whenever they are found to be defective. These tests shall be performed by a qualified backflow prevention device tester, and all test results will be provided to the water purveyor within 72 hours after the test is made.
B. 
Records of such tests, repairs and overhaul shall also be kept and made available to the water purveyor and the Local Health Department upon request.