Does your dishwasher drain completely, or is there always about an inch of water that in the bottom? Before you call a repair service, here are three simple things you can try that will take all of 15 minutes.
Check the filter in the dishwasher's tub
Although most new dishwashers now have small built-in grinders, pieces of food (like popcorn) and even paper (like labels washed off jars) can still clog the filter.
You'll find the filter either in the bottom of the tub, surrounding the base of the lower spray arm, or at the back (like the one shown). The latter has a cage held in place with two screws. Clear any trash away from the filter and, if necessary, remove the two screws holding the filter cage, clean it and check inside for debris.
Check the drain hose
First, disconnect the power by either unplugging the dishwasher or turning off its circuit breaker. Then remove the toe-kick (the panel near the floor). The toe-kick is held in place by two or four small screws. Loosen the hose clamp and disconnect the drain hose (usually it's the one with ridges) from the pump.
Try to blow through the hose (Photo 2) to make sure it's clear. If it's blocked, look for any kinks in the hose and straighten them. Also check the disposer inlet or pipe where the dishwasher drain hose connects under your sink. On older disposers, this inlet is prone to corrosion buildup. Clear the corrosion with a small screwdriver.
Test the drain valve
Most, but not all, dishwashers have a drain valve that keeps water from draining back into the dishwasher. If you have a valve bracket (Photo 3), your dishwasher has a drain valve. To test the valve, push on the valve bracket
to make sure it moves freely. If the valve's frozen, the electrical solenoid that controls it is burned out and
New manufacturer parts are usually available from appliance parts sources. Sometimes you can get a much less expensive used part from a used-appliance dealer. Search the Internet for “appliance parts” to find both.