This is for a friend of mine who just called me.

He said he replaced a kitchen sink garbage disposal for someone. He is not
a plumber. The person called and said the sink wasn't draining and the
original garbage disposal was apparently bad and was making tons of noise.
So, he put in a new one.

Before the changeover, the sink would barely drain at all -- with or without
the garbage disposal running.

Now, with the new garbage disposal installed, the sink still barely drains
at all -- except that, with the garbage disposal running, it drains
perfectly. He tried snaking out the drain line past the garbage disposal
but he didn't encounter any clogs and that didn't change anything.

He is left with a new garbage disposal in place and a sink that won't drain
unless the garbage disposal is running.

Additional info:

1) He said it's a "Badger" (maybe) garbage disposal -- I am about to Google
that and look for an installation manual; and,

2) He said something about a plastic pop-out piece (I think for the
dishwasher drain) that he popped out.

But, is there something else with a new garbage disposal that needs to be
removed or done so the sink drains properly without the garbage disposal
having to run?

Any other thoughts or suggestions?

Thanks.