Place a stopper in a work or utility sink, and lay the screen in the sink. Pour bleach into the sink, completely covering the screen, then set a timer for five minutes.
Pull the screen out of the bleach when the timer goes off. Keep the screen in the sink above the bleach. Scrub both sides of the screen with a scrub brush.
Set the timer for five minutes again. Place the screen back into the bleach to soak. After the five minutes, pull the drain plug out and let the bleach drain out of the sink.
Rinse the screen with hot water, using a hose or spray attachment. Sprinkle dishwasher detergent on both sides of the wet screen, and scrub with the scrub brush. Rinse the detergent off the screen with hot water.