Use a damp dishcloth or a piece of kitchen towel to wipe up any food scraps in the bottom of the dishwasher on top of the sump filter. Leaving bits of food on your dishes, cutlery or cookware increases the likelihood of material ending up in the filter; always scrape food into the garbage or disposal before starting a wash.
Open the dishwasher, slide out the bottom rack and wash the filter with warm water, cleaning away any tough scraps with a soft cloth. Avoid scourers or other harsh cleaning supplies. Rinse off any remaining detergent and slide the lower rack back into position.
Remove the screws and lift out the filter every year to check for debris trapped in the macerator. Clean out any fine debris that has passed through the filter screen with a gentle cloth and replace the filter cover. Check beneath the filter screen if the dishwasher produces a pump-out error code.
Have a plumber inspect the dishwasher's standpipe or drain if the filter and sump are clear of debris but flooding still occurs. It's possible an object from another source, such as the kitchen sink or washing machine, has blocked the piping and caused the drain problems.