Just had a new garbage disposal installed in my single kitchen sink. (Bosch dishwasher drains into this disposal.) Big problem w/ old disposal was sink/running water would collect up to the top before it began to drain. Had/have to run disposal to clear the reservoir every time I use the faucet; otherwise g.disp. Sits full and will smell. Disposal only lightly used per instructions for almost 10 yrs; no drain problems detected when new disposal was installed today. I didn't have (or at least notice) this issue for the first several years I owned the old one, but concerned now that it's still happening w/ new one. Can anyone say if this is normal? Or what may be the culprit? Thanks.

The culprit is a partially blocked drain. Not the disposals fault.

Harold nailed it.
You have a blockage in the horizontal drain line in the wall. Remove the "J" bend from the trap and send your snake up into the wall, (see image) You will rum into a bend about 8 inches in but once around that you only have 6 more feet to put out. Flush with a sink full of hot water. Good luck, Tom

Could not find way to post follow-up to yesterday's Q re this problem, so here goes:

Thanks, Harold and Tom! We ran a snake to its fullest extent through the outlet pipe behind the sink; the line proved clear. Also ran hot water through the line for several minutes.

However, the faucet water still collects to the top of the disposal (just under the rubber gasket/baffle) before it will begin to drain. Once the disposal is full of water when the water is running, it drains fine. However once the water is turned off, the disposal remains full.

That said, we think we have identified a possible explanation - what do you think:

Turns out that the outlet pipe behind the sink is the same height as top of the water sitting in the disposal. The height of the outlet pipe was not a problem some years ago when the kitchen sink was regular depth (8"), but a few years ago it was replaced with a deeper (11", I think) Franke bow sink (single). So we are wondering if because the disposal now sits a few inches lower than previously (i.e. no longer sitting above the outlet pipe but now about even with it), the water according to the laws of nature must sit in the disposal.

Reminder that when we run the disposal, it empties quickly. And when we run water, it does drain fine once the disposal reservoir is full.

So - does this extra info prompt any new/additional thoughts on this?

Til an expert gets here, sounds like the drain where it goes into the wall needs to be lowered to keep disposal from being full of water, you will still need the Trap.

I think you have correctly diagnosed the problem. The water will not flow out until it reaches the level of the drain pipe. The only correction is to lower the drain pipe. To post a response use the "Post Quick Answer" space, just as if you were answering your on question.

There's another solution besides removing the sink, cabinet and tearing into your wall to lower the stubout. Simply replace the present sink with one the same size as before. Good luck, Tom

Appreciate everyone's fast, helpful responses!