Basement plumbing vent

I know there is tolerances on how far a vent is to be from a drain, but I have a question and was wondering, the plumbing for this shower, sink, and toilet was going into the concrete floor and I couldn’t see any venting pipes (this had drop ceiling and saw no pipes going up walls). What is the farthest away the main stack could be from these drains?

Brian,

Did you see a stack penetrating the roof above this area?

The answer your looking for is…5 Feet.

“Click to Enlarge”

I agree, I looked in the IRC book and that what I came up with also. Just have difference of agreement with seller. Thanks for the pic also