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Thread: I've come to the conclusion salt is eating my flagstone

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    I've come to the conclusion salt is eating my flagstone

    This year I have been dealing with a very fine dust that has invaded my pool. It gathers on the creases in the liner, corners, depressions, etc. I can brush but it reappears after a day or two. Vacuuming helps but it comes back a few days later. The pic makes it look black but it is actually brown (not chocolate brown but weak coffee brown). My numbers are perfect and and for the most part always have been. The pool is 3 years old and has been SWG and BBB since it's birth. I battled mustard algae once but have no cc's or OCL.

    I sealed my stone coping (Arkansas Flag) at the start of the first year. I have not sealed it since. I also did not have this issue until this year. I am assuming I am seeing very fine dust being eaten off the stone by the salt. Some of the stones do look like they have some surface deterioration.

    I recently added two coats of sealer and hope I am not too late.

    I really don't have a question. I was just throwing this out there for informational purposes. Any comments would be appreciated though. Especially if you have dealt with this same issue in your own pool.

    Cheers,
    Steve
    Attached Images Attached Images
    18' x 36' saltwater inground vinyl pool

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: I've come to the conclusion salt is eating my flagstone

    While your stone dust theory is plausible, it isn't the only possibility, nor even the most likely. Usually when there is salt damage to flagstone you see obvious flakes chipping off, not only extremely fine dust.

    What you describe sounds like dead algae, which often "rains" down on the bottom of the pool when the FC level is just slightly too low for your CYA level. It could also be some kind of pollen, though that seems rather less likely if you haven't seen it in previous years (though that doesn't rule out pollen).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Re: I've come to the conclusion salt is eating my flagstone

    I have seen flakes off the top. As well as some cracks in the edge ( the 3" thickness part when you are in the pool looking at it ). Also, on some of the stones the top is pitted slightly. These took the most sealer when I recently resealed them.

    I actually keep my fc a little high for my CYA level (if I understand things correctly).

    My current numbers are:
    fc 6 (in some hot Arkansas sun)
    cc 0
    ph 7.5
    ta 60
    cya 50
    Borates 30
    ch have not checked in a while
    18' x 36' saltwater inground vinyl pool

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    JasonLion's Avatar
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    May 2007
    Location
    Silver Spring, MD
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    37,879

    Re: I've come to the conclusion salt is eating my flagstone

    Alright, your FC is indeed fairly high for your CYA level, and given the flaking of the stone, that does push stone dust right to the top of the list.

    By the by, nothing to do with your dust issue, but your SWG will last longer if you use a slightly higher CYA level. We recommend CYA between 70 and 80 for use with a SWG.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  5. Back To Top    #5

    Re: I've come to the conclusion salt is eating my flagstone

    I will double check with an OCLT. If it is negative I will raise my CYA and lower my FC. After that bout with Mustard Algae I was gunshy and kept my FC levels up. Lord forbid I wouldn't wish mustard algae on anybody!
    18' x 36' saltwater inground vinyl pool

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    Join Date
    Jun 2012
    Location
    Minnesota
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    12

    Re: I've come to the conclusion salt is eating my flagstone

    I found your post interesting as we have first encountered the same fine brownish dust in the bottom of our SWG pool this year. We vaccum but then it's back again in a day or two. We don't have flagstone coping, never had a mustard algae problem - knock on wood...We do have an auto cover and we were first thinking it was coming off the cover when we open and close it. This is also our 3rd season. We used to throw in our Polaris maybe twice a week to vaccum but now we almost have to do it daily because of this settlement in the creases and around the drains.
    2010 18' x 40' IG, SWG
    27,000 gal, vinyl liner
    Jandy Aquapure salt chlorinator
    Mineral Springs Salt Sanitizer
    Jandy CL460 cartridge filter system
    Polaris pool cleaner
    Coverstar auto safety cover

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