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Thread: acid damage to rocks, or scale?

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    jeffreymlewis's Avatar
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    acid damage to rocks, or scale?

    Hello,

    About a week ago I noticed what looks like calcium scale on one rock near my pool. Thing is, the white marks are way above the water line. This rock is near (within 2' of) the area where I drop chemicals (Cl, HCl, etc...).

    Is it possible these white marks are damage caused by muriatic acid? If so, how can I prevent this from spreading? I've already brushed the rock and sprayed with copious amounts of water. (After brushing, the white marks disappear for a while, then reappear after the water dries.)

    Here are some pictures.







    Thanks,
    Jeffrey
    15k gal, IG painted plaster (black), 3.0 HP Intelliflo VS, Pentair CCP240, MiniMax 400, build date unknown (estimate 1995), attached spa w/ water fall

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    duraleigh's Avatar
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    Re: acid damage to rocks, or scale?

    That looks like efflorescence....... minerals migrating to the surface from behind and evaporating/precipitating once they reach the surface.

    Muriatic acid will clean it off. I don't think there is a cure other than time
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: acid damage to rocks, or scale?

    Rocks are natural and absorb the minerals from the pool water. What you are seeing is calcium. Also into the mortar joints.

    Try acid washing with a strong solution 1/3 acid water and a stiff brush. It should form or bubble.

    Then balance your pool after the acid gets into the pool water.
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    jeffreymlewis's Avatar
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    Re: acid damage to rocks, or scale?

    Ok cool, I'll give it a try. Thanks for your suggestions!
    15k gal, IG painted plaster (black), 3.0 HP Intelliflo VS, Pentair CCP240, MiniMax 400, build date unknown (estimate 1995), attached spa w/ water fall

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