Clogged Gargabe Disposal (?)

We are having problems with our Kitchenaid KaDette Disposal unit. We have a single basin, with a dishwasher attached.

After we run the unit, we get water (not clean, with some debris) that comes back up into our sink after draining. It will then sit for a while, but gradually has drained. When we run the unit, the water drains normally, however it has been coming back.

I assumed a clog, and have tried using a plunger, but to no avail.

Can anyone offer me any advice? Please help ... I would really like to avoid a plumber bill right now! Thanks

A plumber that has an electric powered snake is really your best option. Save your money and don't bother with chemical concoctions. Their perfomance stinks!

Sounds like a clog deep in the drain system limiting the flow rate. The disposer pressurizes the waste stream to some extent, and since it can't go downstream it backs up, probably rising up the vent. Once the disposer shuts off, the waste slowly drains, part to the sewer, part back into the disposer.

If you're handy, you could take the trap apart and clean it manually, but it's not likely that the trap is the problem. The pro with the snake is your best bet. He (or she) could better determine where the problem really is and fix it appropriately.

Thanks Mikey and Redwood. For the plumbing neophyte ... any idea what I can expect to pay for the "snaking"?
Also - what about the "biological" drain cleaners? Anyone know if they work? Are safe, or just more of the same?