Get rid of stubborn green and black stains with Wet and Forget Outdoor. Just dilute with water, spray it on, and forget it. The Wet and Forget Outdoor Concentrate is ideal for precise applications on surfaces such as sidewalks, retaining walls and fencing. Wet and Forget works over time with the rain and wind to gently clean up moss, mould, and mildew on virtually any outdoor surface. No scrubbing or rinsing required. In most cases, surfaces stay clean for 1+ years after treatment of Wet and Forget.  The Wet and Forget Concentrate makes 12 liters total. Wet & Forget is bleach-free, non-acidic outdoor cleaner.