I covered my 16x40 weather-treated deck with Quick Cap composite planks six years ago and tried cleaning it with Simple Green mixed with bleach, which didn't work very well. I found Corte Clean during an Internet search, saw the reviews and ordered some. The first cleaning was the most difficult but every year I'm getting more familiar with how it works. I found that using warm water and a paint mixing attachment on my battery drill works best to dissolve all the cleaner granules. I spray with a one gallon Chapin sprayer, keeping the deck wet all the time then doing a little scrubbing with a stiff brush on tough spots. One bag of Corte Clean can do my whole deck. I'm extremely pleased!