I've just replaced the pretty simple plumbing under the kitchen sink, i.e. two drains into a T, then trap, then out through the rear wall and into basement. I replaced all the existing OLD pipes with PVC. Everything went together pretty smoothly, but something (I'm thinking obvious) must be wrong because water is not draining out. FYI, it drained before I started, I was simply replacing one of the pipes that was corroded and split. Any thoughts?

I don't know much about plumbing and if this does not relate to your question I'm sorry, just trying to help. Could you plunge the sink? Maybe it's a clog. Use a new plunger or use and old one but bleach it before and bleach the sink after

Sounds like you might have dislodged some debris built up in the pipe walls and now you have a clog in the horizontal drain in the wall. The solution would be to snake the line. Remover the trap and send your snake up into the wall,(see image) You will run into a bend about 8 inches in but once around that you only have 6 more feet to go. After. Flush with a tub full of hot water. Good luck, Tom