Greetings.

I just replaced my bathroom sink and have hooked the plumbing back up.
The one problem I have is that the PVC pipe that leads into the drain
trap from the wall pipe (which is iron).

I am using the same pvc pipe that existed there with my old sink. When
I run water and let it drain from the sink water seems to get backed up
and leaks back from the wall/iron pipe to the wall and runs down to the
floor. Am I missing something? I am pretty sure that everything is
the same leading back into the main house plumbing.

Any ideas or suggestions would be appreciated.

Thanks.

Chad