Periodic cleaning of our WPC decking is suggested, even if it appears clean, is important to prevent the build-up of pollen/debris that can cause mold. If unsure about the product being used to clean/remove stains from your deck, it is recommended that you test a small area in an inconspicuous place to determine if the product will cause any unwanted discoloration. Using a spray nozzle may use commercial pressure washers to remove stains, ground in dirt, or mold. Don not use steam nozzle. Use cold water and keep the spray nozzle at least one foot away from the deck. The use of a pressure washer with a greater than 1500 PSI and / or applied closer than 10 from the deck surface could damage the decking surface and result in a loss of warranty coverage.