About once every two months I sit a wee juice glass half full of bleach in the upper tray of the dishwasher ...facing up.... and at the same time I wash the two filters in the bottom "floor" of the compartment .... only thing, where I did not look was the area right along the hinged area where the washer door attaches to the box ... it was disgusting... I just assumed my bleach wash and every other wash would reach that area. My mistake. I wash all dishes by hand ..but the hubby uses the dish washer.. I should have been checking. Heads up!