Grease, oil and sand interceptors shall be provided by and at the expense of a property owner when, in the opinion of the director of public works, they are necessary for the proper handling of liquid wastes containing grease in excessive amounts, or any flammable wastes, sand or other harmful ingredients; except that such interceptors shall not be required for private living quarters or dwelling units. All interceptors shall be of a type and capacity approved by director of public works, and shall be located as to be readily and easily accessible for cleaning and inspection.