What should I do if my dishwasher won't drain properly?

Check the drain air gap or in-sink disposal for clogs. Remove the air gap cover and plastic cap, then clean out any debris with a toothpick or brush. For the disposal, verify that the knockout plug has been removed. Also check that the drain hose is not kinked, pinched, or crushed behind the dishwasher. Ensure the drain hose is at least 12 inches and within 40 inches from the base of the dishwasher.