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Thread: Sediment/Crystals on pool bottom

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    Sediment/Crystals on pool bottom

    During the winter I noticed a lot of sediment on the bottom of the pool; it was deep enough in places so that when critters were squirming it would leave tracks. I'm in the process of opening and notice that my auto pool bottom cleaner (my 3yo calls it "the dude") if filling up with this white crystal sediment. What is it and is it normal? Did I add too much of something last season? I don't remember it from last year. I assume it's excess something coming out of solution because of the cold water. Here are some pics of what I'm talking about:
    25000 IG Plaster; Jandy DE 48 sqft filter, 120 gpm; Jandy 1.5hp

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    Re: Sediment/Crystals on pool bottom

    Welcome!

    Is this a salt pool?
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    Re: Sediment/Crystals on pool bottom

    No, regular chlorine.
    25000 IG Plaster; Jandy DE 48 sqft filter, 120 gpm; Jandy 1.5hp

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    Re: Sediment/Crystals on pool bottom

    Can you post a complete set of test results? Is your water currently clear?
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    Re: Sediment/Crystals on pool bottom

    Quote Originally Posted by duraleigh View Post
    Can you post a complete set of test results? Is your water currently clear?
    This.

    I'd also like to know what happens to this stuff when you put it in a glass of hot water...
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    Re: Sediment/Crystals on pool bottom

    Is it hard or soft?
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    Re: Sediment/Crystals on pool bottom

    FC 15
    CC 1
    TA 90
    CH 225
    CYA 40
    pH >7.8

    Very Clear. In the process of slamming.
    25000 IG Plaster; Jandy DE 48 sqft filter, 120 gpm; Jandy 1.5hp

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    Re: Sediment/Crystals on pool bottom

    A
    Quote Originally Posted by Wrobert View Post
    FC 15
    CC 1
    TA 90
    CH 225
    CYA 40
    pH >7.8

    Very Clear. In the process of slamming.
    Ok, nothing too drastic there. What all did you use for treatment last year again? What might be different about what happened in past seasons?
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    Re: Sediment/Crystals on pool bottom

    Last year was the first year of the pool, had it installed the fall before. Followed the methods of this site for treatment, nothing out of the ordinary, (bleach, borax, acid) were my biggest additions. The test results were good all season; the only issue I had was keeping the pH down.

    The crystals are hard, not sure how they will dissolve in hot water, I"ll check later. They are flavorless, if that matters....
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    Re: Sediment/Crystals on pool bottom

    Quote Originally Posted by Wrobert View Post
    They are flavorless, if that matters....
    Well that is always a good test
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    Re: Sediment/Crystals on pool bottom

    I don't believe the forum has seen anything quite like that in 8 years or so of posts. I am just bumping the post to keep it in the forefront until we can figure out what it is. How much volume would you say there is in your whole pool? 1 lb? I don't even know whether it should be lbs or fluid ounces. Very interesting and probably not the least harmful. I think it will simply go away on it's own but I hope we can identify it first.
    They are flavorless, if that matters..
    Yeah, if you had said, "Delicious", that would have changed the whole conversation!
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    Re: Sediment/Crystals on pool bottom

    I had something similar to this last year (though not as much) and I thought it was "excess salt" that was settling out. But my salt level was never high. My ch was a bit higher than yours. I will have to look at my spreadsheet from last year when I get home this weekend.


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    Re: Sediment/Crystals on pool bottom

    Sorry to say it, but I'm at a loss for a definite answer.

    I would suggest setting a small pile aside and putting a few drops of Muriatic acid on them. Do that, and tell us what happens please. Set aside another pile if you still have some. I may ask you to send me a handful if you'd be willing and able.
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    Re: Sediment/Crystals on pool bottom

    If acid doesn't cause the crystals to foam or bubble, it may be that it is calcium sulfate crystals.
    Does your tap water contain a lot of sulfates? Or do you use dry acid a lot?

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    Re: Sediment/Crystals on pool bottom

    We need ChemGeek in on this one, but from some reading I would posit: Calcium Sulfate. If so, how it got there and how to get rid of it is beyond me....

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    Re: Sediment/Crystals on pool bottom

    If it is Calcium Sulphate, you would might guess at dry acid use or high Sulphate makeup, because it contains Sulphur compounds.
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    Re: Sediment/Crystals on pool bottom

    Thanks for all of the input. I don't have any Muriatic on hand but I tried some vinegar; it bubbles and dissolves the crystals. I'll be getting some Muriatic and will try that if necessary. Not sure if our water contains alot of sulphates, how would I tell or find out. As far as the acid I used, only Muriatic last year. I put some in a cup with near boiling water and they SLOWLY appear to be dissolving.
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    Re: Sediment/Crystals on pool bottom

    I think they may be borax crystals. Just out of curiosity, how much borax did you use last year?
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    Re: Sediment/Crystals on pool bottom

    A little more info: after putting it in the hot water the crystals seem to have dissolved but don't appear to be going into solution. If I stir the water it becomes milky when I leave it set, it clears and the fine sediment settles to the bottom. Kind of like the consistency of DE. See pics below. As far as Borax I believe I added about one box (2lbs I think) last spring.

    25000 IG Plaster; Jandy DE 48 sqft filter, 120 gpm; Jandy 1.5hp

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    Re: Sediment/Crystals on pool bottom

    More info about the possible origin of the crystals.
    http://aquamagazine.com/content/post...-Crystals.aspx
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