Chlorine Bleach or Sodium Hypochlorite (active ingredient in Chlorine Bleach) based deck cleaners that the uneducated recommend may appear to quickly remove mildew (white in color) and mold (black and other colors) fungus from Timbertech and other Composite Decking. Nothing could be farther from the truth.
The Environmental Protection Agency (EPA) and the Occupational Safety & Health Administration (OSHA) DO NOT RECOMMEND Chlorine Bleach for Mold (Mildew is a species of Mold) remediation on porous surfaces such as Timbertech and other composite decking.
The reason for this is that Chlorine Bleach does not remove or kill the roots (mycelium) of the fungus, but actually waters them. A few weeks after you have cleaned a deck with chlorine bleach or sodium hypochlorite based products you will notice the mildew or other mold fungus growing back in greater numbers, especially after additional moisture comes into contact with the deck. It will make the problem worse and harder to remove the next time the composite surface becomes unsightly.
In addition, Chlorine Bleach products reek havoc on the rest of the deck structure shortening the life of the entire structure. It is highly corrosive to any metal including structural connectors or fasteners (screws) holding the deck together. It shortens the life of the pressure treated lumber supporting the deck. This could lead to liability issues for the owner of the property and any company who recommends its use.
PRODUCTS THAT CONTAIN SODIUM HYPOCHLORITE ARE ENVIRONMENTALLY DESTRUCTIVE. It is shocking that Timbertech and other composite manufacturers do not follow the recommendations of the EPA or OSHA and recommend one of the most TOXIC chemicals known to this earth.