Phisherman wrote:
I need to tap into a PVC 4" waist line about 12" up off a basement
concrete floor. Unfortunately or fortunately, a cleanout is in this
desired location and that's where I want to install a drain for a 28
gal. laundry tub with a 1.5" PVC trap. What materials/steps are
needed to do this properly and cheaply? Thanks

Unscrew the CO plug and screw in a male adapter.
Then you can stack PVC fittings onto that.
I would put a 4 X 2 WYE or TEE/WYE fitting first
so that you can still have a CO fitting.
Then branch off from the 2" inlet to the sink drain
(reduce to 1.5", if desired).

NOTE: If this 4" stack carries waste from above
(baths, etc.) the new sink drain will need a vent
on the downstream side of the trap. You *may* be
able to get away with a mechanical (Studor) vent.

Jim