A mixture of 1/3 cup powdered laundry detergent, 2/3 cup trisodium phosphate cleaner, 1 gallon of water and 1 quart of household bleach removes mold and mildew from vinyl siding and gutters. Leave the mixture on the siding for 10 minutes, and then rinse off completely.
Cover any plants in the area with plastic prior to treatment. Working from the bottom of the vinyl siding to the gutters, apply the cleaning solution with a pump garden sprayer. After the treated area has soaked in the solution for a short time, brush the siding with a soft-bristled brush, then rinse the area off with water, working from the gutters downward.