All backflow prevention assemblies existing at the time this ordinance is adopted which do not meet the requirements hereof shall be excluded from the requirements hereof, provided they were approved for the purposes described herein at the time of installation and have been properly maintained. Such previously- existing assemblies shall be subject to the periodic inspection and testing required by subsection 8-2-6B of this chapter. Whenever an existing assembly is moved to another location or requires more than minimum maintenance, or where it is determined to constitute a hazard to health, the unit shall be replaced by an approved backflow prevention assembly. (1985 Code § 18-1-17)