There are many reasons why a dishwasher may become clogged and not drain, including problems with the drain hose, blockages in the kitchen sink or garbage disposal, items in the dishwasher pump or filter, or other, more serious problems. Resolving these issues can potentially be achieved through some troubleshooting steps, although if the problem is major in scope, such as a broken pump, professional repair may be necessary.
Check the drain in the kitchen sink and clear as necessary. Run the garbage disposal, if possible, to help clear the drain system.
Examine the connection between the garbage disposal unit and the hose that connects to the dishwasher. Remove the knockout plug at that connection point, if it has not already been taken out during installation.
Remove the lid from the air gap, if applicable, on the kitchen sink. The air gap looks like a little metal dome. Remove the hoses inside the air gap and rinse with water to clear any obstructions. Connect the hoses to the air gap and close the lid.
Turn off and unplug the dishwasher. Pull the bottom rack out of the dishwasher and look inside the bottom of the dishwasher tub. Clear away any foreign objects or food debris that may be clogging up the dishwasher pump. Turn the filter, if the dishwasher has one, in a counterclockwise motion and lift up to remove. The filter will look like a round, plastic device. Wash the filter with cold water and replace.
Lift out the bottom spray arm from the dishwasher tub. Look inside the unit for the wash impeller, which looks like a little plastic fan. Clean away any objects that may be blocking the motion of the impeller.
Remove the drain hose from the rear of the dishwasher and inspect for possible obstructions. Clean the inlet screen in the hose and the inlet screen at the dishwasher connection point. Connect the drain hose firmly and straighten the hose out.
Examine the drain valve near the rear of the dishwasher and clean the solenoid, which is the lever that moves the drain valve open and shut. Make sure the solenoid to ensure it can move properly.
Call a service professional if the above methods do not resolve the issue, as repair may be necessary.