White film on limestone coping

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Peachtree21

Member
Sep 17, 2022
6
Atlanta
Greetings all,
Have a question that hopefully someone can shed some light on. Our pool was built and finished last June. We used limestone coping (salt water pool) and the coping only (deck is a sandstone) shows quite a bit of white haze. Any ideas? Thanks all. IMG_7621.jpegIMG_7623.jpegIMG_7622.jpeg
 
It’s efflorescence, not mold. Happens with all types of limestone and flagstone materials. Moisture is wicking up through the mortar bed from the pool walls (as well as splash out and rainfall) into the material. The water wicks up to the surface and leaves deposits behind that are white (calcium and other minerals). Happens to my flagstone coping all the time.

You have to seal porous stones to avoid moisture but sealants have their own set of issues. It all depends on how much effort you want to expend.

There are efflorescence cleaners for stone work but they are fairly expensive and if you don’t seal the stone after cleaning it then you’ll be right back to square.
 
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Peachtree21 said:
Thank you. I did have it sealed right after install of that makes any difference.
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Good to know. The other possibility is that the sealer is breaking down and causing some of the chalkiness you see.

Sealers really only work if the entirety of the stone is sealed before it is installed and then a sealer (usually a high quality penetrating sealer) is applied every year or so. The gunite bond beam also needs waterproofing before anything is attached to it (tile, coping, etc). Unfortunately this is a fight against Mother Nature and laws of physics and chemistry … no one ever wins that fight.

You can try the Wet & Forget and see if it helps. No harm in doing that. But I have see this all before and I’d bet a box of donuts that it won’t work.
 
JoyfulNoise said:
You can try the Wet & Forget and see if it helps. No harm in doing that. But I have see this all before and I’d bet a box of donuts that it won’t work.
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Wet & Forget does not have eggs in it and is probably less cost than the donuts.
 
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