Have a 2 bowl sink...one side has a disposal and the other doesn't.
We keep experiencing water backing up into both sides of the sink. I
took apart the plumbing underneath and there didn't seem to be any
clogs. If the sink is backed up, I'll run the disposal and water will
disappear from that side of the sink but come up the other side. The
only way to get the water down is to plug the non-disposal side and
use a plunger on the disposal side and do this about 1/2 dozen times.
It almost seems like there's some kind of vacuum occuring but I'm not
much of a plumber and don't know what to do. Any advice on what could
be happening?