During a wash cycle, food scraps wash off plates, cutlery and cookware and into the bottom of the dishwasher. To stop this material entering the drain and causing blockage, the perforated screen acts as a filter, removing material too large to pass through its holes. The screen is also useful should something break in the wash.
At the end of the wash cycle, empty the dishwasher and pull out the lower rack. The perforated screen is visible in the bottom of the dishwasher below the lower spray arm. If a small amount of water is in the bottom of the appliance, bail it out with a cup. If the filter is blocked, you will see food scraps on the surface.
A clean filter allows only water to pass through. Wipe away bits of food sitting on the surface of the screen with a kitchen cloth and clean up any other material sitting in the bottom of the appliance. Lift the cup assembly on top of the filter to remove it from the dishwasher. Rinse the upper and lower filters under running water and use a gentle nylon brush to clean away any hardened accumulations of dirt. Use warm water mixed with a little dishwasher detergent to help remove stubborn stains.
The filter must be re-inserted before the appliance can be safely used again. Rinse the filter of any remaining suds, drop it back into its slot and slide the lower rack back into position. Make a note to repeat this process once a month regardless of whether you have another blockage. Ensure that the filter is properly seated and run the dishwasher on a normal cycle without any dishes to clean the racks and walls.