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Thread: Gritty substance

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    Gritty substance

    Good morning, it's been a while since I've been on. Bought the big test kit and things have been going well. Sorry I haven't needed you, but now I have an issue again....

    I've noticed a gritty subtance on my pool bottom and sidewalls. They feel like sand paper and this is on a vinyl pool. I'm guessing hardness level. I have the good test kit but I wanted to start in the tight direction so I started here. The water is crystal clear.


    15x32 vinyl oval
    1 hp, sand filter

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Gritty substance

    Welcome to TFP!

    That sounds very much like calcium scaling, which results when some combination of PH, TA, and CH are high. Please post a complete set of water test results so we can confirm that is what is happening.
    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

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    Re: Gritty substance

    230 ta
    250 ch
    8 ph
    3 cl


  4. Back To Top    #4

    Join Date
    Jul 2012
    Dumfries & Galloway, Scotland

    Re: Gritty substance

    Your Langelier Index is scoring in the region of +1.0, indicating a likelihood of scale formation.

    You need to get TA under control by aeration. learn how in Pool School pool-school/lowering%20total%20alkalinity, you will also need a substantial amount of acid to lower pH whilst you aerate.

    pH of 8.0 is rather high, bringing down TA, to target levels will help you control this better.

    CH levels of 250 aren't really a big concern, but it may well be a good idea to think about lowering your CH levels, as they are not required in Vinyl Pools.

    Have you tested your fill water? It is important to know what you are putting into your pool, as this will have an effect on your pool chemistry, for example hard water areas will have high levels of TA and CH from underground water sources.

    Stuart Murray
    Scotland UK

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