Fire hydrants shall measure not less than twelve inches from finished grade to bottom of lowest hydrant outlet. Fire hydrants shall be installed at a maximum distance of four hundred feet apart. Fire hydrants shall be installed of a design, layout and location approved by the city engineer and fire chief, and in accordance with standards adopted by the National Board of Fire Underwriters entitled, “Standard Schedule for grading Cities & Towns of the United States with reference to their Fire Defenses and Physical Conditions,” Edition of 1956. (Ord. 143 § 2(part), 1960: Ord. 89 § 6.2(f), 1955).