Stack Vent

Definitions

Stack vent is an arrangement of group venting when fixture traps are vented through the soil stack which terminates into a header or open air and no additional venting is required.

For a better explanation go to 1.1.3.2.(1)

Installation Requirements (7.5.2.1.)

1. The stack must be a soil stack of minimum 3" size that extends as a stack vent that means no discharge from any other fixture located on any other higher storey.

2. All stack vented fixtures must be located at the same floor.

3. The maximum number of stack vented fixtures is 6.

The lowest fixture in a stack vented group is a water closet.

The maximum number of water closets in a stack vented group is 2.

The maximum number of other fixtures connected above the water closet is 4.

4. Where two water closets installed, they must be connected at the same level to the stack.

All other fixtures must be connected directly and independently to the stack above the center line of water closets and the uppermost fixture must be connected to the vertical portion of the stack.

5. Where there is only one water closet in a stack vented group, it may connect to the vertical stack or horizontal continuation of the stack and remaining fixtures upstream of the water closet must be connected directly and independently to the stack and the uppermost fixture must be connected to the vertical portion of the stack.

6. The total number of fixture units connected above the water closet is 8.

7. Maximum size of a fixture drain connected above the water closet is 2".

8. No siphonic trap connected above the water closet is permitted.

Additional Requirements

1. The developed length of a fixture drain measured from the trap weir to the stack is 2 pipe diameters minimum or 1500 mm maximum.

2. maximum fall is 1 fixture drain pipe diameter

3. maximum change of direction is

1. 1350 for a P-trap,
2. 2250 for a S-trap.

4. No other drainage pipe may connect to fixture drain between the fixture trap and its protective vent.

5. The fittings used to connect the two water closets to the soil stack may be

1. Double Combination Y and 1/8 Bend or Double Long Turn TY
2. Double Y & two 450  elbows

consult Table 7.2.4.5.

6. Requirements that fixtures must be connected "above the center line of the water closet" permit the installation of a combination drainage fitting:

Only bear in mind that this fitting is not mentioned

in the Ontario Code and Guide for Plumbing

7. If there is a need to connect an additional fixture to the stack where a stack vent is installed, the fixture drain must connect below the water closet of the stack vented group and the fixture trap vent can connect back into the stack above the flood level rim of the highest fixture, or terminate into  header or in open air.

7.5.3.1.(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, a vent stack that does terminate in open air outside the building.

1. at the same floor

2. at the floor as a result of alteration