Vent pipe and fittings for the venting system shall comply with the provisions of Article
V.
The protection of trap seals from siphonage
or back pressure shall be accomplished by the appropriate use of soil
or waste stacks, vents, revents, back vents, loop vents, circuit or
continuous vents, or combination thereof, installed in accordance
with the requirements of this Chapter, so that at no time shall the
trap be subjected to a pressure differential of more than one inch
of water.
Hydraulic gradient. Fixture drains shall be
vented within the hydraulic gradient between the trap outlet and vent
connection, but in no case shall the unvented drain exceed the distance
provided for in Table 860-150A, "Distance of Fixture Trap from Vent."
A single wall hung water closet shall have the three inch soil, or vent stack directly in back of closet, or have a separate two inch vent, and when closets are located above one another, each shall have a separate two inch vent in back of each closet, except the upper most closet will not require a separate two inch vent provided it connects directly to the stack vent. When more than three wall hung water closets are located on one horizontal branch, they shall be provided with a circuit or loop vent as provided for in §
860-156A in addition to the two inch vent directly in back of each closet, but no other relief vents will be required. Wall hung water closets shall have a separate two inch vent in back of each closet, except that two closets back to back may have a common two inch vent.
Combination of fixtures on one horizontal branch.
When two water closets, two floor drains, or two similar floor-level
connected fixtures, or any combination of these fixtures are located
on one horizontal branch of the building drain, they shall be provided
with a proper size relief or loop vent.
Individual vent as common or dual vent. A common
or dual vent is permitted for two fixture traps when installed on
a vertical continuous waste and vent, or stack vented when the highest
fixture, provided both fixture drains connect with the vertical drain
or stack on the same level and within the distance allowed between
a trap and its vent.
Soil and waste stacks in building have more
than 10 branch intervals shall be provided with a relief or yoke vent
at each tenth interval installed, beginning with the top floor. Where
an odd number of floors above ten are involved, they shall be equally
divided. The size of the relief or yoke vent shall be equal to the
size of the vent stack to which it connects. The lower end of each
relief or yoke vent shall connect to the soil or waste stack through
a wye below the horizontal branch serving that floor, and the upper
end shall connect to the vent stack through an inverted wye or tee
not less than three feet above the floor level.
No vent shall be required for a rain conductor
trap, backwater trap, area drain, sub-soil catch basin trap, or any
outside drain. For further clarification of venting procedures as
outlined in this chapter, refer to illustration in Chapter 22.