On Sep 20, 9:31*am, wrote:
I'm installing a 4-ft. kitchenette with sink and, due to space
constraints, I am considering running 1-1/4" abs as opposed to
1-1/2" (the lines will tie into 1-1/2" about 8' downstream). *What
problems might I run into wrt to draining? *TIA!

Current min drain pipe (in the wall, not under sink) is 2".

My older home (1930) had some 1 1/2 lines that over the years were
problematic. I had all the cast iron laterals replaced with 2" ABS.

This sounds like a bootleg / non-code project.

Most code changes (modernization) are for safety or improved
performance but there are millions of old installations that work just
fine that aren't up to current code.

A drains at 1 1/4" (for any appreciable run length) are pretty
small.
I think you'd have trouble depending on sink usage (garbage disposal?)

Even 1 1/2" is rather small on a long length run....I would suggest re-
thinking your design & work in 2", the result will more trouble free.

cheers
Bob