I currently have a vent that runs up the wall behind the toilet, then makes a turn going roughly parallel for about 5 feet until it meets the edge of the house, then turns and heads up to the attic. From this, there's a wye, located about 2 feet from where the vent exits the concrete, and then the sink drain is tied to this. Before questioning begins, does this make sense as I've explained it? See first picture attached.

So what I want to do is put another bend in the vent... as shown in the second picture. Reason for this is I want to put a recessed shelving area where the vent currently is. Is this allowed?

Is there a special type of elbow I should use or special type of wye I should use? I guess I shouldn't have to touch the current wye, since my re-running is above that. Also, any sort of special slope requirements? As you can see, the current horizontal runs have some slope to them, and the pictures are all approximations.

Your offset looks OK to me. You may install any fittings to your vent stack as long as you don't choke off the air flow and slope back to the main. While they make a vent ell that's a shortest radius you are not required to use it. Regards, Tom

The first horizontal run heading towards the attic vent is about a foot, then the vertical section is approximately 5 ft. Then, the final run over to the vertical attic run is another 6 ft. That's the approximate distance. I had assumed that this would be fine, since I'm not extending any of it... just adding bends. Sounds good to me.

When you say "as long as you don't choke off the air flow and slope back to the main" are you saying that as long as the slope is as pictured, I should be good to go?

Just for my personal knowledge, are all wyes the same? I know sizes vary, but I mean angles and things like that. I want to have as much info as possible before heading to the local HD since they always have everything in the wrong box, all of which is mislabeled, with employees who typically can't tell their left hand from their right (no offense to anyone who may work there, but from my experience, most, not all, of their employees aren't the best at answering questions).

When you say "as long as you don't choke off the air flow and slope back to the main" are you saying that as long as the slope is as pictured, I should be good to go?
Yes, You're fine.

Are all wyes the same?

A wye's a wye! They're all the same. Regards, Tom

As usual, thanks!