Trex or trex like material

[tunatussle 14]

Customer had deck built about 2 yrs ago and builder went out of business so she does not know what product was used. The deck now has black spots the size of a half dollar that look like oil stains. Not sure how I wan to approach the problem Have been thinking of bleach and washing. Any other ideas how to solve ?

[Celeste 341]

It's mildew! Housewash mix should handle it just fine.

Celeste

[Beth n Rod 1,279]

If bleach does not handle it, then it is tannin bleed which can be lightened with citric acid. But...the stains may return again. It is the nature of the beast with this type of decking material that due to composition, the stains are produced from within.

Rod!~

[YVPW 20]

You might have to X-jet some bleach and soap on there at around 5 to 1. It depends on what downstream injector you have. Your injector might not get a strong enough solution on the surface.