I installed my ChoiceDek decking about 5 years ago and was totally discouraged when it showed mold spots on it within a few months. When I called the manufacturer, they recommended using a bleach product (Jomax) and to leave it on longer than the package directions showed. I did that, and the spots returned faster than before. Power washing didn’t help, nor did having it cleaned professionally. Not until I used Corte-Clean was I satisfied with the appearance of my deck. Not only did it come cleaner than ever, but it lasted much, much longer than I could have hoped for. From September till June! Although in June I had to clean it several times for the product to stop coming up discolored. I’ll do better next time. Soooo happy with your product. (By the way, the manufacturer’s customer service rep let me think my oak trees were responsible for the staining instead of being the result of nature’s effect on their product.) And, PS, they are STILL recommending Jomax or Olympic Premium Deck Cleaner (containing bleach). It seems to me they don’t want happy consumers. I know that if I hadn’t found Corte-Clean I would have already replaced my deck!