The first and most critical step is ensuring safety. A dishwasher is connected to both electricity and water. Therefore, before any inspection or repair, turn off the dishwasher at the circuit breaker (or unplug it) and shut off the water supply valve located under the sink. Failure to do so risks electrical shock or flooding. Once these precautions are taken, remove the lower dish rack to access the drain area at the bottom of the tub.

The most frequent site of a clog is the dishwasher’s internal filter. Modern dishwashers have a self-cleaning or manual-clean filter system located under the bottom spray arm. Remove the spray arm (usually by unscrewing a central cap or releasing a clip) and then take out the filter. This cylindrical or mesh component is designed to trap large food particles. Wash it thoroughly with hot, soapy water and a soft brush. You will likely find a buildup of grease, broken glass, or food debris. Reinstalling a clean filter solves a surprising number of drainage problems.

A related but often overlooked issue is the connection point to the garbage disposal. If your disposal is clogged or its drain knockout plug has not been removed, water cannot exit the dishwasher. Run the garbage disposal for a few seconds to clear any backup. Then, detach the dishwasher drain hose from the disposal’s inlet. Inside the disposal’s nipple, you will find a small, metal plug. Ensure it has been knocked out; if not, use a hammer and screwdriver to punch it into the disposal (then remove the loose plug). Also, clear any built-up grease or food from this inlet.