§ 156.50  TRAPS.
   (A)   All fixtures shall be separately trapped and traps placed as near as practicable to the fixtures and, in no case, shall a trap be set more than one foot from its fixture, except by the permission of the City Engineer. No traps shall be placed in drain or in any soil or waste pipe in such place that they will interfere with the free circulation of the outside air from the fresh air inlet through pipes to house or to outlet above roof.
   (B)   All traps shall be one of the forms known as "S" traps unless special permission is given by the City Engineer to use another form. Every trap shall be separately vented and protected from syphonage by branch ventilating pipe connecting with the main drain line or ventilating pipe, as before specified. These vent pipes shall be attached to the crown of the trap where practicable. They shall not be less than two inches in diameter for water-closet traps, nor less than one and one-fourth inches for other single fixtures, and one and one-half inches for two fixtures, and two inches for any number of fixtures more than two. Where a closet and three or more other fixtures using one and one-half inch traps or less are vented by the same branch vent pipe, the pipe shall be increased to not less than three inches. The venting of a water-closet may be omitted in the discretion of the Plumbing Inspector, when the waste pipe with which it is connected is not less than four inches in diameter at all points, and the distance from the outlet of the closet to the branch in the main waste pipe does not exceed two feet. Vent pipes shall in all cases be of extra heavy cast-iron, galvanized wrought iron or brass pipe, except immediate connections with traps, which may be of lead.
(1967 Code, §§ 16-24, 16-25)  Penalty, see § 10.99