All it takes is one spray and stubborn exterior stains from mold, mildew and algae go away. There's no rinsing or scrubbing needed. Just apply and walk away and let Jomax® Spray Once® do the work. The bleach-free formula works with wind, rain and moisture over time to remove unwanted stains on fences, siding, roofs, concrete and more. Jomax® Spray Once® gal is concentrated and makes up to 5 gal of ready to use formula. Simply combine with water in a garden style pump sprayer and begin cleaning.