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Thread: crystallization in gunite pool

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    crystallization in gunite pool

    Hi Everyone, we opened the pool up yesterday and today while I was vacuuming the pool I noticed small crystals, much larger than what pool salt typically looks like on the walls and floors of the pool, It is extremely difficult to scrap off and safe to say almost impossible, I am wondering if anyone has any ideas as to what this could be, I will be leaving the pump on and chlorination at 100% over the next 24 hours but unlikely that the crystals will disappear.

    The only thing we added to the pool when opening this season was Chlorine, salt and algaecide.

    If anyone has ideas please share.
    Pool:30x50 58,00 gallon gunite, SWG: Hayward with 40k T15 Cell.

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    Re: crystallization in gunite pool

    Almost definitely calcium carbonate scale. Can you post a full set of readings from opening the pool? Was the pH high?

    Get some of the crystals and put a drop of acid on them. If they're calcium carbonate, they will bubble and fizz when combined with acid.

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    Re: crystallization in gunite pool

    The readings are:
    CC: 1
    FC: 1
    PH: off the charts
    CH 240
    TA: 110

    any ideas?
    Pool:30x50 58,00 gallon gunite, SWG: Hayward with 40k T15 Cell.

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    Re: crystallization in gunite pool

    Your CSI is too high which can cause scaling. Pool School - Calcium Scaling


    You need to reduce your PH down to 7.5 with some acid ASAP. Use pool math to determine your CSI and how much acid you need to add. CSI is sensitive to PH.


    Also, what is your CYA?
    Karen
    33K IG w spa plaster, Pentair 1HP Whisperflo, DE Filter, SWG CircuPool RJ-60, Dolphin Triton Plus, Raypak Dig 336K BTU, TF-100.
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    Re: crystallization in gunite pool

    Quote Originally Posted by kcindc View Post
    Your CSI is too high which can cause scaling. Pool School - Calcium Scaling


    You need to reduce your PH down to 7.5 with some acid ASAP. Use pool math to determine your CSI and how much acid you need to add. CSI is sensitive to PH.


    Also, what is your CYA?
    I am not sure what csi is but cya is 0
    Pool:30x50 58,00 gallon gunite, SWG: Hayward with 40k T15 Cell.

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    Re: crystallization in gunite pool

    It looks like you actually have 2 issues.

    1. calcium Scale

    2. lack of sanitation.....solve this one first

    Using powdered granules, raise your CYA to around 30 ppm using PoolMath. Then, with liquid chlorine (shut off your SWG) please raise your FC to 12 ppm and hold it there by testing and re-dosing.

    I would not bother with the the calcium scale until you get a grip on sanitation.

    read "The ABC's of Pool Water Chemistry" up in Pool School for some background and then read the "SLAM" article. You will have lot's of questions but we'll answer them all.

    The scale issue can wait although you would be ahead of the game if you lower your pH down to around 7.4 or so.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Mod Squad pooldv's Avatar
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    Re: crystallization in gunite pool

    More on scale here, Pool School - Calcium Scaling
    More on CSI here, Langelier and Calcite Saturation Indices (LSI and CSI)

    Keep it between 0 and -0.3. Poolmath will calculate it for you.

    Save this info for later and get the pool cleaned up first.
    TFP Moderator
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: crystallization in gunite pool

    Quote Originally Posted by pooldv View Post
    More on scale here, Pool School - Calcium Scaling
    More on CSI here, Langelier and Calcite Saturation Indices (LSI and CSI)

    Keep it between 0 and -0.3. Poolmath will calculate it for you.

    Save this info for later and get the pool cleaned up first.

    I bought some chlorine pucks and jimmy rigged it in a basket it in the pool with two pucks. I have a salt cell but since I do not get home until around 8 in the evening I thought it would support the existing salt cell. I hope I did not do anything that would somehow damage anything in the pool.
    Pool:30x50 58,00 gallon gunite, SWG: Hayward with 40k T15 Cell.

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    JamieP's Avatar
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    Re: crystallization in gunite pool

    Quote Originally Posted by pooldv View Post
    More on scale here, Pool School - Calcium Scaling
    More on CSI here, Langelier and Calcite Saturation Indices (LSI and CSI)

    Keep it between 0 and -0.3. Poolmath will calculate it for you.

    Save this info for later and get the pool cleaned up first.
    Is there a reason to recommend -0.3 for the bottom value instead of the -0.6 as listed in PoolMath?
    28,000 gallon freeform, Stonescapes Tropics Blue Minipebble with abalone, 3.5' to 8.5' depth. 2 skimmers, 5 returns, dedicated vacuum port, Dolphin Z5 robot. All Pentair equip: EasyTouch 8, IC60 SWG, VS pump, 520 Cartridge Filter, 3 Intellibrites, 2 Color Cascade Bubblers. TurboTwister Slide and 8' Salt System Jump Board. TF-100. My Jan-Mar 2016 build:
    Waxahachie, TX Owner Build - A race to beat the baby!!

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    Re: crystallization in gunite pool

    If it goes more than -0.3, poolmath does say "potential to become corrosive to plaster".

    Maybe the wording should be changed from -0.6.

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    Mod Squad pooldv's Avatar
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    Re: crystallization in gunite pool

    I don't typically recommend -0.4 to -0.6 unless scale is present and needs to be dissolved, gently. It isn't that difficult to keep it in 0 to -0.3 window. And a swing in PH can move it out of the range so it gives a little buffer.
    TFP Moderator
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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