: : : : Can a toilet be vented behind the 3" horizontal drain pipe it goes to or does it have to be downstream of it?
: : : 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
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