Any existing backflow preventer shall be allowed by the utility to continue in service unless the degree of hazard is such as to supersede the effectiveness of the preventer, or result in an unreasonable risk to the public health. Where the degree of hazard has increased, as in the case of a residential installation converting to a business establishment, any existing backflow device must be replaced with an approved device suitable for that degree of hazard. (Ord. 347 § 8, 1995).