Hasa 75121 1 qt Bottle Stain-Out 12 per case. Stain-Out when added to fresh pool water, will hold potential stain-causing particles in suspension. This will inhibit stain and scale formation on pool walls, floors, and tile surfaces. Stain-Out can also remove existing surface staining. Swimming can be resumed immediately after applying. Adding Stain-Out at recommended dosage will neutralize the metallic ions of magnesium, iron, copper, and scale in pool water to remove and prevent stains. For severe stains, pour in water directly over affected area. Stain-Out will remove and help prevent stains for six months or more.