: : : : : : Reply:
: : : : : : The vent fitting needs to be downstream of the toilet drain.
: : : : : : Good Luck. e-plumber

: : : : : What can happen if it is behind the toilet drain?

: : : : sorry about all the posts

: : : Reply:
: : : What can happen is if there's a clog in the line, the clog or part of the clog can possibly move behind where to toilet drain ties into the horizontal line, the clog will be cleared by snaking the line from the toilet drain. Something can stay stuck in the vent fitting. Then you'll have a toilet with an inoperable vent.
: : : Good Luck. e-plumber

: : What if 2 sinks would drain in directly behind the vent

: Reply: From UPC
: Vent must be downstream of the trap (exceptions)[905.2]

: I'm not sure which code you need to follow, for better advice, contact a local licensed plumber.
: e-plumber

Thanks for your help