Do what "Yoyizit" stated. Pour two quarts of water into the side with the disposer, let it sit, and time how long it takes to drain. After this drains, I would remove the "P" trap only part of the drain, put a bucket/something under the open pipe from the disposer, and pour another two quarts into the sink to see how long it takes for the water to run out. IF the water runs out quickly, I bet it does, then the problem is beyond the "P" trap. Now "Mr. Chips" comes into play. Could be a clogged vent stack. Could be something in the drain after it enters a wall. Do you have a dishwasher? I've found a few that the lines were coated with a gummy/soapy material creating a small internal diameter=slow drainage. This was due to dishwasher soap(s). David
Last edited by Thurman; 08-24-2010 at 09:48 AM.
Reason: more info