Failure of a dishwasher to drain may be linked to several problems, both within the dishwasher and the kitchen itself, as the dishwasher is linked to the kitchen drainage system. When a dishwasher won't drain, there are several factors to check and clean before attempting to force the dishwasher into a drain, but the steps may solve the problem without the need for a professional service call.
Clean the kitchen sink and run the garbage disposal.
Take the lid off the air gap, if one is present. An air gap looks like a small metal or plastic dome and is usually installed on the rear or side underneath a kitchen sink. The air gap prevents waste water from the dishwasher and the kitchen sink from mixing, but the air gap hoses can get clogged, leading to dishwasher drain problems. Disconnect and clean out the hoses inside the air gap by flushing them out with water to remove debris. Reconnect the hoses inside the air gap and close the air gap lid.
Disconnect power to the dishwasher and locate the drain hose, usually found in the rear of the appliance or behind the front lower kick plate. Remove the drain hose from the dishwasher and clear the hose out to remove obstructions, shaking the hose firmly to help dislodge blockages. Place the hose in a straight line when reconnecting the hose to the dishwasher to prevent bends or kinks in the water flow line.
Look inside the dishwasher for objects, residue or debris in the bottom of the dishwasher tub that might be blocking water flow from exiting the dishwasher. Clean as needed.
Reconnect power to the dishwasher. Close the dishwasher door firmly.
Turn the control knob to "Drain" on applicable models and then press or select "Start." On electronic panel models, select a normal wash cycle and press "Start." Wait 10 seconds and then press "Start/Reset" to force the dishwasher into a drain cycle.