Whenever the city deems a service connection's water usage contributes a sufficient hazard to the water supply, installation of an approved backflow prevention assembly shall be required on the lateral service line of the consumer's water system, at or near the property line, or immediately inside the building being served, but before the first branch line leading off the lateral service line in any event. The type of protective assembly required shall depend upon the degree of hazard existing at the point of cross-connection. The city shall require that a test be performed on all testable backflow prevention assemblies after the initial installation in order to determine their adequacy. (1985 Code § 18-1-17)