Where automobiles are serviced, greased, repaired or washed or where gasoline is dispensed, separators shall have a minimum capacity of 6 cubic feet (0.17 m
3
) for the first 100 square feet (9.3 m
2
) of area to be drained into the separator. Parking garages in which servicing, repairing or washing is not conducted, and in which gasoline is not dispensed, shall require a triple basin. Areas of commercial garages utilized only for storage of automobiles are required to be drained through a triple basin.