Please Assist!! Adding second vent/soil stack

hello all
i am adding a second 3" vent/soil stack in the south end of the house. main vent/soil stack is in the middle of the house about 25ft downstream. previous owners installed WC, bathtub, vanity in basement with no venting. since i am redoing 2nd floor room, main floor kitchen, and basement bath, i thought to add this second line to vent and drain all the new and old stuff. please see the attached sketch. I think I am ok, except where the WC is involved. Do i need to add a vent line off this back to this new vent stack? Any help is appreciated.
cheers

I'm not sure what you have in mind, but what you have drawn shows the lower fixtures without vents, the second fl. shows three connections without vents. The line on the left of your drawing shows a bathroom at the third fl. if you hook it up that way you destroy the vent on the lower level, keep in mind the UPC requires a individual vent or a piping arrangement that serves the same purpose on all fixtures. I think you need to redisign, sorry. (not sure what code you use)

You should vent something.
If it's plumbed like the drawing, you will have flooding everywhere, and the sewer gas will smell pretty bad.
There is nothing there that can be fixed.

It should look more like this on a two story

still trying

thanks guys... getting closer. Ontario building code says no vents if within 5ft of the line, but i have redirected the kitchen drain line as per your comments. existing bathroom on second flr is of course already vented into that separate soil stack. i made some modifications to the sketch - see attached. let me know if i am getting there.
cheers

The way you have it drawn, NOTHING on the lowest level is properly vented. Being within 5' of a line, by itself, does not avoid the need for a vent. It depends on WHAT the line is. If it is a drain, then it cannot be used as a vent, in most cases. A minor point is that the vent "Y" between the stack and the sink trap is drawn backwards.

am i getting closer?

hj / terry
thanks for you insight so far. had a plumber in today - estimate with supply lines was $5k + so i will be powering on solo. i revised the sketch and vents based on ontario code re wet vents, etc. take a look and let me know your thoughts.
cheers

That looks a lot better.

You should have a 2in. vent comming off your toilet.