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Thread: Can shock damage/discolor a gunite pool?

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    Can shock damage/discolor a gunite pool?

    First of all thanks to everyone for making such a great site. I will read and reread all the stickys and be sure to get you complete readings if I have a pool calc question. The pool calculator is awesome!



    Quick question,
    Can adding shock by sprinkling or broadcasting the granules on the surface of the water permanently damage or discolor a pool? The granules settled to the bottom of the pool and turned it a brownish color. After about 4 hours of direct sunlight it was significantly lighter but still marked. I imagine that over the next few days the spot will go away and the pool will be ok.
    We are now mixing the shock with water BEFORE adding it to the pool.

    Thanks for all the replies.
    Southern Girls Pool- In ground, 18X36 vinyl liner, approx 27K gallons with sand filter, booster pump for polaris, and Jandy gas heater in Mississippi

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    JasonLion's Avatar
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    Welcome to TFP!

    Yes, powdered/granular shock products can damage the pool surface if the powder/granules do not completely dissolve before reaching the bottom. However, this normally only happens after repeated applications over a period of time. Rapidly appearing brown stains are not the usual effect. I am not sure what is happening in your situation.

    It is always best to pre-dissolve such products (but not calcium increaser) before adding to the pool.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Jason, I'm curiuos why not to dissolve calcium increaser (CaCl)?
    30K gallon, In-ground Gunite
    Central NJ

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    Mod Squad JohnT's Avatar
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    Quote Originally Posted by akelley
    Jason, I'm curiuos why not to dissolve calcium increaser (CaCl)?
    I believe the calcium increaser heats up when added to water.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    JasonLion's Avatar
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    Calcium chloride and calcium chloride dihydrate get hot when they dissolve in water, occasionally very hot. If you put a lot in a bucket and add water there is some chance of burning yourself or melting the bucket. You can simply distribute them across the surface of the pool and the large volume of the pool will distribute the heat enough that it is insignificant.
    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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