My kitchen sink won't drain. The drain runs through an old disposal, then into a trap and down a drain pipe. I pulled the trap off and the sink drained. Thing is, there was no water in the drain pipe (at least none that I could feel). Am I just not reaching in far enough to check for water, or could my disposal be bad? I managed to get a snake about two feet down, but I'm not sure that that would be far enough if there is a clog.

last question, If there is a clog, it would be from potato peels my wife pushed down the thing (I know not supposed to put potato down a disposal). Is there something I can pour down the thing that would dissolve the potato?