Hello all! I'm new here from Illinois. Found this site while trying to figure out how I was going to run the sewer lines in my basement. Was hoping someone here would be able to help.

Below are pictures of what I have in my basement. I will be installing a tub/shower and a toilet on one side. On the other I will have 2 sinks. My question is how do I know if the tub and toilet drains are vented? Also can I dumb the sinks into the 2" pipe (which I believe runs up to vent the bath upstairs) or do I have to use the 3" pipe that the upstairs tub and toilet dump into? Any answers will be greatly appreciated. Thanks!
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