Every garage, automobile service station, repair shop and car washing rack maintained in the city and having connection with the sanitary sewer system of the city for the disposition of wastewater, shall have installed on the waste line from the car wash sump a suitable sand and grease trap that will effectively prevent entrance into the sewer system of sand and grease, and shall be constructed substantially to conform to state health department design for the same. The traps shall be skimmed of oil and grease at regular intervals, and shall be kept in proper operating condition at all times. (2000 Code § 5-206)