tapping into buried 2" drain line

As part of a basement remodel I'm planning out the rough-in for adding a bath on slab, residential dwelling. I'm going to connect a lav drain line line to an existing below slab 2" PVC buried line. I'll be adding a 2" horizontal 'Y' to the existing line and I've heard PVC repair couplings are notorious for not getting a water tight weld. I'm checking with the city if I can use shielded couplings.

Alternatively, although I hate adding four 90 degree sweeps to a horizontal line, I could reroute the line to accomodate the new fitting as in the attached drawing? The existing 2" line services only a single bar sink.

thanks for any advice

Attachment 18577

There's a limit on the total number of degrees you can turn a drain before a cleanout is required, and I think that would exceed it. WHy not just put a wye in the straight existing pipe? You do need to maintain the 1/4" per foot drop, and offsetting things might let you achieve that, but it shouldn't be a major deal most of the time.

I would install a wye off the line, using mission couplings that are schedule 40 size. And no, they don't leak.
We use them all the time. Adding that many 90 bends is asking for trouble.

http://www.terrylove.com/images/mission_bandseal.jpg