The pressure washing does help with under the lanai as well, but it never gets as bright as the one's out in full sun. It always has a more dull look and then the rust look eventually creeps back in. I have another product that I am going to try that our yard guy actually uses. Side note......we have the same Aqua Gray marble pavers as a walkway up to our front doors and our front porch. Interestingly enough, they do not have the same rusting issue as our pavers on our pool deck. The only difference that I am aware of is the one's on our front porch and walkway do not have any sand that they were laid on. They are strictly cemented down on concrete. Anyhow.....I say all this because our yard guy came and treated our yard and whatever he sprayed on the yard, he got on our Aqua Gray walkway. The next morning our walkway was all rusted in color. I nearly died. The owner of the company immediately came out and brought this really powerful liquid. As soon as it was sprayed on, the orange rust color completely went away. Here is the before and after picture as well as a picture of what he used. So I am going to try it on the pavers under our pool deck lanai and see how it works. You can get it at Lowe's or Home Depot. I wish you all the best of luck. We love our pavers but unfortunately I think it is going to be a constant battle. We'll see how it looks a few years from now :)
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Great advice regarding sand for marble patio pavers
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