Your dishwasher line should have a "reverse trap" in the line. That is the line should make an upside down "U" before it enters the garbage disposal. This prevents any waste from the disposal unit from backflowing into your dishwasher. The remaining plumbing all seems to be installed correctly.

Who has eight urns laying around for plumbing issues?

Yes the dishwasher drain needs a 20” loop, strap to back of cabinet high as possible..
Plumbing is fine. Sounds like blockage or vent issue. Did they use sink as a wash out for materials?
Is it and island sink or a bar sink on a peninsula.? I would pull trap check trap, run cable. If supply lines are flex or spray nozzle reaches reassemble trap after cable and run water to Check drainage. Trees above vent? Hope this helps

I would never hook up the drain like that I would put a y on the drain on the clean out on the end of the Y and on the 45 side run the Trap underneath the disposal that's [censored] job I hope your Plummer didn't do that

+1

If you don’t flush line after cabling, reassemble fill both basins and drain both At the same time

PM sent your way.

Yep

[quote=JWRid]Your dishwasher line should have a "reverse trap" in the line. That is the line should make an upside down "U" before it enters the garbage disposal. This prevents any waste from the disposal unit from backflowing into your dishwasher. The remaining plumbing all seems to be installed correctly. [/quote
This, or just loop the dishwasher drain hose so it works like a p trap.

I have known lots of plumbers and they all tell me the same thing....people don't chew their corn!

Mine is same also. Never had any problems draining at all. Your P-trap is probably full of something. take apart and clean it out. do that before renting a snake. Easy to do, just put a drip pan of some type to catch the water.

Agreed. In the past we regularly had problems with stopped up drains.Our slummer is not a fan of waste disposals. He recommended we stop using the disposal. We rarely have drain problems now.