This is a long story... I have a 5 year old Trex deck. Trex does not tell you how really ugly the deck gets and how hard it is to clean. Many people of complained about this. Last year I discovered this wonderful product and have not been happier. The first cleaner I used was recommended for composite deck and was a chlorine based product that was super expensive, la or intensive and solution expired in 30 days. It also did not get out all the mold and mildrew. I should mention I live in western Washington and it is wet here. Okay. So I get my little bag of Corte Clean and think how in the world is this going to be enough to get my deck clean. I pout the powder into my sprayer and spray on. Leave it on for 30 minutes and then wash off. I did scrub a little bit on tough spots. Now I noticed there were still stains and was a little disappointed but low and behold it rained a couple of days later and deck was cleaner. Consequently each time it rain the deck improved. I was pleasantly surprised. I even sprayed products on my Hardiplank siding and fence and it worked wonderfully. My neighbor put in Trex and had exact same problem....no other composite deck cleaners work as well as Corte Clean. I only wish that Trex would have put that information ontheir website when I was researching composite decks and cleaners. The key to happiness with this product is reading the directions and waiting for deck to vet wet in my case by rain which reactivates the product. Best of luck to this company and customers. Thank you for listening.