7.5.4.

(1) The upper end of every soil or waste stack shall terminate in a stack vent and the stack vent shall terminate in open air outside the building, or connect directly or through a header to another stack vent or vent stack that does terminate in open air outside the building.

(1) Except as provided in Sentence (2), every soil or waste stack greater than 4 storeys in height shall have a vent stack.

(2) A soil or waste stack that serves as a wet vent does not require a vent stack.

(3) The vent stack required by Sentence (1) shall be connected to a vertical section of the soil or waste stack at or immediately below the lowest soil or waste pipe connected to the soil or waste stack.

(4) Fixtures may be connected to a vent stack provided,

(a) the total hydraulic load of the connected fixtures does not exceed 8 fixture units,

(b) at least one fixture is connected to a vertical portion of the vent stack and upstream of any other fixtures,

(c) no other fixture is connected downstream of a water closet,

(d) all fixtures are located in the lowest storey served by the vent stack, and

(e) the section of the vent pipe that acts as a wet vent conforms to the requirements regarding wet vents.

(1) Except as provided in Sentence (4), where a soil or waste stack receives the discharge from fixtures located on more than 11 storeys, a yoke vent shall be,

(a) installed for each section of 5 storeys or part of them counted from the top down,

(b) installed at or immediately above each offset or double offset, and

(c) sized in accordance with Sentence 7.5.7.5.(1).

(2) The yoke vent shall be connected to the soil or waste stack by means of a drainage fitting at or immediately below the lowest soil or waste pipe from the lowest storey of the sections described in Sentence (1).

(3) The yoke vent shall connect to the vent stack at least 1 000 mm above the floor level of the lowest storey in the section described in Sentence (1).

(4) A yoke vent need not be installed provided the soil or waste stack is interconnected with the vent stack in each storey of the section in which fixtures are located by means of a vent pipe equal in size to the branch or fixture drain or 2 in. in size, whichever is smaller.

(1) A soil or waste stack that has a nominally horizontal offset more than 1 500 mm long and above which the upper vertical portion of the stack passes through more than 2 storeys and receives a hydraulic load of more than 100 fixture units shall be vented by an offset relief vent connected to the vertical section immediately above the offset, and by another offset relief vent,

(a) connected to the lower vertical section at or above the highest soil or waste pipe connection, or

(b) extended as a vertical continuation of the lower section.

(1) The trap arm of a fixture that has a hydraulic load of not more than 1 ½ fixture units may be connected to the vertical section of a circuit vent, additional circuit vent, offset relief vent, relief vent or yoke vent, provided that,

(a) not more than 2 fixtures are connected to the vent pipe,

(b) where 2 fixtures are connected to the vent pipe, the connection is by means of a double sanitary T fitting, and

(c) the section of the vent pipe that acts as a wet vent conforms to the requirements regarding wet vents.