We have a Trex deck located in Minnesota that is approximately 10 years old. We bought it because it didn't need to be painted so it would last. After about a year, it started getting black mold spots all over it. We went online and found out Trex was known for this problem. Had I known Trex had this problem, we would have rather installed a wood deck and just painted it. We contacted the Trex company and they were not helpful. We went to Lowe's and discovered Corte Clean. Unfortunately, it was beyond its expiration date, and didn't work! I called the Corte Clean company on a Saturday and they resolved the problem. Corte Clean is the only stuff that got the deck clean. Lowe's no longer carries it, so we order it from the company. We have now been using Corte Clean for 10 years.