Rust stains around pool deck?

A customer of mine had this pool put in about 5 years ago and says these rust looking stains have been showing up in the past couple years. He says they look a lot worse this year and his pool cover is not any sort of metal, he doesn’t use pesticides, and like myself, does not know where they are coming from. Here’s a few pictures of the stains. Has anyone experienced anything similar before? Any help is really appreciated.

I don’t think it’s rust . But it’s easy enough to check if you have oxalic on the truck. If not go to sherwin Williams and pick up some wood brighter it’s the same thing.


That’ll most likely be the first thing I try when I go back. It was a cold morning when I was their so I didn’t even attempt it. If I’m not mistaken, oxalic won’t really work well if at all in the cold weather. Tried on some recent rust stains on a newer driveway last week and the they didn’t even budge.

I’ve never had an issue with cold weather effecting the OX but I’m in Florida so that might be why

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Could just be my lack of knowledge. It was about 40°F out…just enough to wash I’d say. You ever feel 40°F before? Lol jk. My grandparents live out in Estero FL. I’m aware it gets sort of chilly their sometimes. Not sure if that cold though.

When it gets in the 20s here even the yankies won’t go outside. It’s a different kind of cold down here .its a wet cold Layers don’t help .


So no one has come across anything similar before eh? Any guesses? I have a job a few doors down next week I’ll stop by afterwards and give oxalic a shot and probably another rust remover. Hoping my chemical provider has something similar to f9 barc available.

Doesn’t look like rust. More like pigment in the concrete.

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I agree with @APW1

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But wouldn’t that show up once it was finished? He said they just started showing up a couple years ago and getting worse with time. The pool cement is around 5 years old.

@gbattle might know.

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Not really. It has a fresh smooth finish. The more it gets pressure cleaned, the more it can be exposed. Like driveways. It’s usually more noticeable when wet.

Hm. This was the first time he had it cleaned. It looked the same before I started and it being wet didn’t make it appear any more than dry.

@gbattle any thoughts or idea?

I’m not sure if this helps but, Kool-Deck is what we are looking at in these pictures. It goes over the concrete around pools to keep the surface cool enough to walk on. This Kool-Deck also has a stamped decorative pattern to give it the stone look. Most stamped and kool decking has no UV protection in the sealer or color and in time it all fades.


:point_up_2::point_up_2::point_up_2: :sunglasses:

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Moisture underneath causing staining ?

That very well may be the answer. Thanks @gbattle!

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