Wet Venting Clarifications

[Timothy Witt]

Hey guys, thanks for the forum, it has helped me countless times.

We have a question about wet venting. Every image in the plumbing codes we can find shows an offset toilet when wet venting. We want to know if there is any issue with connecting to a line directly underneath of the toilet. It seems like installations go out of their way to not route the upstream fixtures this way, but we can't find the reason why. Is Option 1 allowable, and if not, why? Thanks!

Edit: Assume the water closet is connected with a wye fitting, not a tee. My diagram didn't make that very clear.

 

[Terry]

You can't drop a toilet into a santee on it's back. The poop goes goes upstream and plugs the uphill line.
You are way better off installing a 90 below the toilet and then bringing that into a wye that directs the poop down the line. If you have ever pulled a toilet that was dropping into a santee, it would disgust you.

 

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[Timothy Witt]

Thanks, Terry! Does the same apply dropping it into a combo instead of a santee?