need to reattach roof drain leader to sealed standpipe "mystery drains"

[Belmondo]

I got dinged by the city for having the leader off a porch roof draining to the sidewalk (not my work, and I understand the safety reasons for the code). Clearly the previous owner disconnected the leader from the sewer system to do this, and I need to reattach it. Lots of question now. What the heck am I looking at here in the basement under the porch? Was the right the drain and the left a cleanout? And for that matter how do these drains attach to the main? There must be a trap, no? Otherwise that floor drain would stink. But what keeps the trap on an leader drain wet? Do they depend on regular NJ rain? But if the leader was removed, shouldn't that trap now be dry even though it doesn't stink? Or did they do something rash like cement it up? That looks like what they did to the cast iron hub on the right.

So which of these doors do I try, the left capped one that looks like it was oakum packed and lead poured, or the right cemented one?

[hj]

The left one is probably a cleanout for the floor drain. The right one is the right size for a "leader" connection and was just plugged with concrete to keep stuff out of the pipe.

[gellfex]

Thanks hj, but what's the story on how it's trapped?

[hj]

With a "P" trap, just like most floor drains. THe leader probably does not have one, because it it did it would fill up with debris from the roof. In those days they did NOT worry about "trap primers".

[Belmondo]

But under normal circumstances the floor drain would not be in use and it's trap would go dry. And what about that leader going directly to the sewer? That makes the top of the leader on the porch an open vent that is NOT at the roofline and below the windows of the upper 2 stories. That can't be code!

[Belmondo]

deleted irrelevant