(a) 
The length of a vent stack or main vent shall be its developed length measured from the lowest connection of the vent system with the soil stack or waste stack to the following points:
(1) 
The vent stack terminal, if it terminates separately in open air; or
(2) 
The connection of the vent stack with the stack vent or common vent, plus the developed length of any such common vent from such junction to a terminus in open air.
(b) 
Every vent stack or main vent shall have a diameter determined in accordance with the following table based upon its developed length and the number of fixture units connected to the soil or waste stack vented by it; provided that such vent size shall never be reduced by more than 1 pipe size, except as permitted in the following table:
TABLE B. SIZE AND LENGTH OF VENTS FOR SOIL AND WASTE STACKS
Size of soil or waste stacks
(in)
Fixture units connected
Diameter of vent
(in)
1-1/2
2
2-1/2
3
4
5
6
8
Maximum developed length of vent (in feet)
1-1/2
8
150
 
 
 
 
 
 
 
2
12
75
300
 
 
 
 
 
 
2
24
70
300
 
 
 
 
 
 
2-1/2
42
35
140
450
 
 
 
 
 
3
30
20
80
260
650
 
 
 
 
3
60
20
80
260
650
 
 
 
 
4
100
 
35
100
260
1100
 
 
 
4
250
 
30
95
240
1000
 
 
 
4
500
 
22
70
180
750
 
 
 
5
550
 
 
28
70
320
1000
 
 
5
110
 
 
20
50
240
750
 
 
6
 
 
 
 
20
95
2420
1000
 
6
 
 
 
 
18
70
180
750
 
8
 
 
 
 
 
30
80
350
1100
8
 
 
 
 
 
25
60
250
800
10
 
 
 
 
 
 
30
80
350
10
 
 
 
 
 
 
25
60
250
(1965 Code, sec. 15-150)
(a) 
Individual and relief vents shall not be less than 1-1/2" in diameter. For 1-1/2" wastes, the vent shall be of the same diameter as the waste pipe. For 2" or larger vents, the vent shall not be reduced by more than one pipe size except that not more than one water closet, on a 4" branch waste not over 25' in length, may have a 2" vent.
(b) 
The length of an individual or relief vent shall not exceed the length permitted for a vent serving the same size soil or waste stack as established by table B in section 3.05.211. The length of an individual or relief vent shall be its developed length from its junction with the fixture drain or soil waste branch served by the vent, to its connection with the vent stack or stack vent. The diameter of a circuit or loop vent shall be at least equal to the diameter of the horizontal soil or waste branch served.
(1965 Code, sec. 15-151)
(a) 
Revent stacks from groups of more than five fixtures on a floor in buildings more than two stories in height shall connect into waste stack or waste branch with wyes and 1/8 bends, and shall not connect into the stack or branch above the waste of the fixture it serves. Batteries of water closets or urinals from three to twenty in number in toilet rooms on the same floor shall be vented by the system of loop venting by taking off a vertical stack in front of the first fixture and extending 12" above the highest fixture on that floor and return horizontally full size to main vent stack at the end of the battery, or the vents may continue separately through the roof full size, thus forming a circuit vent system. When fixtures discharge above a branch in a vertical stack, each branch shall be provided with a relief vent at least one-half the diameter of the soil or waste branch and shall be located in front of the first fixture connection. When more than ten closets or urinals in a battery are vented in this manner, there shall be an additional connecting line installed between the waste and vent lines in center of the battery and this connecting line shall be of the same size as the waste line.
(b) 
The revent pipe from all drum traps shall be wiped into waste pipe (Y-branch) not more than 6" from trap seal, and said vent pipe shall not extend horizontally more than 18" from trap seal to the vertical stack. Closet revents shall be connected to a branch of a soil or waste pipe 12" above the highest fixture connected to this stack. Revents to closets may be omitted when closets are not more than 3' from the stack or house drains and the waste does not connect with the stack or house drains more than 2' below finished floor line, and there are no fixtures on floor above wasting into the same stack. When a vent pipe from a trap connects into a vent from another, the connection shall be made at least 1' above the highest fixture connected to this vent on the same floor. The back or revent from any fixture shall not be more than 6" from the trap it serves, measuring from water seal or trap. Quarter bends of 90 degree offsets will not be permitted in vents of 2" size or less when placed at a point lower than the water line of the fixture served.
(c) 
When a stack or vent pipe extends through a roof within a distance of 15' of any door or window opening, the stack or pipe shall be extended at least 2' above the top of the door or window opening. No caps, cowls or bends shall be affixed to the top of any stack or vents; wire brackets may be used. No stack or vent pipe shall extend through a roof within 24" of any fire wall or parapet and no stack or vent shall be encased in any fire wall or parapet.
(d) 
Except as otherwise provided in this article, each and every fixture shall be revented and shall have a water seal trap placed as close to the fixture as practicable. Vent branches, inverted wyes or plain tees conforming to weight for soil pipe fittings as heretofore specified, shall be used in openings left in vent pipes to revent fixtures.
(1965 Code, sec. 15-152)
P traps shall be installed in a continuous waste and vent where possible. When this construction is used and traps are ventilated through the waste fitting, the outlet of such fittings shall not be set below the water seal of the trap. The distance from the trap to the waste outlet opening shall not exceed a developed length of 3-1/2' on 1-1/2" drain or 5' on 2" drain and such drain shall have a grade not exceeding 1/4" fall per foot. The oversizing of a fixture drain to gain length of run will not be permitted. When drum trap, floor drain trap or stall urinal traps are connected to a continuous waste and vent line or stack that serves any other fixture, the continuous waste and vent shall be not less than 3" up to the highest waste fitting, provided that the section of such continuous waste, and vent serving only the waste from one lavatory or drinking fountain may be 2". All fixtures connected to a continuous waste and vent line or stack shall be on the same floor level.
(1965 Code, sec. 15-153)
All soil pipe or stacks passing through roof shall be flashed with sheet lead weighing not less than 3 pounds to the square foot, or ten ounce copper. Flashings shall have the sleeve brought up to top of pipe and turned down on inside of pipe. A roof connection shall be screwed or sweated on end or vent, on 1-1/2" Arco, Byers pipe or, copper tube. Flashings shall extend at least 4" on either side of vent stack and 6" on the upper side. Lead vents shall not extend through the roof but shall be returned to a vent stack. Stack and reventing pipes on outside walls of buildings shall extend straight through the roof and the openings in the roof shall be flashed.
(1965 Code, sec. 15-154)