If, in the judgement of the director, an approved backflow prevention assembly is required (at the customer's water service connection; or, within the customer's water system) for the safety of the city's water system, the director shall give notice in writing to that customer to install such an approved backflow prevention assembly(s) at specific location(s) on the customer's premises. New customers shall install an approved device(s) at the time of building permit issuance or within 90 calendar days after notification to do so. Existing customers shall install approved device(s) within 180 calendar days after notification to do so. (Ord. 92-18 §5, 1992).