Soil Stack Vent

[Matt Werner]

Since most examples show W.C. connected directly to the soil stack, they always show the stack extended vertically as a vent. In this case I will have some 3" branches running through the joists to a vertical drop to the lower level. Two 3" or maybe a 3" and a 2" roof vent covers the required venting as I understand. Just not sure if I need to add a vent at the stack.

 

[Terry]

Most codes call for venting within six feet of a toilet.

 

[Sponsor]

 

[Matt Werner]

Thanks Terry,

No problem with the vents in the bathrooms, I am designing in appropriate venting at all the fixtures. All vents are currently less than 2 feet downstream.

The question is do I need an additional vent at the vertical stack? Once the fixtures are vented, the horizontal run of 50' is ok, but then it makes a turn into the top of the stack and drops 9' to the drain of the house. So many examples show the stack continuing vertical through the roof, that it seems like the stack vent is required, but I can't find it anywhere in the Michigan Plumbing code.

 

[Reach4]

I did not find anything in the IPC against your proposal. I am not a plumber. I did find this, which may be of interest:

https://codes.iccsafe.org/content/IPC2018/chapter-9-vents
903.2 Frost closure.

Where the 97.5-percent value for outdoor design temperature is 0°F
(48°C) or less, vent extensions through a roof or wall shall be not less
than 3 inches (76 mm) in diameter. Any increase in the size of the vent
shall be made not less than 1 foot (305 mm) inside the thermal
envelope of the building.​