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Thread: Algae/Calcium Staining in Gunite Pool

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    Algae/Calcium Staining in Gunite Pool

    Had someone call me asking for advice about their pool. Pool has apparently been sitting unused for two years aince home was purchased. The homeowner recently drained the pool and attempted to remove all the algae from the pool walls. It is a gunite pool by the way. Well, he said that some of the algae is literally in the walls of the pool and he hasn't been able to remove it. He also mentioned calcium?? stains on the pool walls. I asked how old the pool was and he said it was probably installed in 2007 as he bought the house out of a foreclosure. One of the those recent McMansions built.

    Any suggestions on how to get rid of the remaining algae other than filling the pool up, adding shock and algacide and hoping it doesn't spread over the winter? Any thoughts as well on possible calcium deposits on the walls? I don't have much experience with gunite pools, most I see have liners.

    Thanks for your suggestions.

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

    Re: Algae/Calcium Staining in Gunite Pool

    A carefully done manual acid wash should take care of the calcium/algae stains. Algae growing while calcium scaling is happening can indeed become embedded in the walls of the pool. Removing the calcium with acid will also remove the embedded algae.

    The odds are high that some algae will grow over the winter once the pool is refilled, even if the walls are acid washed. There are ways to avoid that but they are more work than simply killing the algae in the spring. Algae will only grow very slowly during the winter because of the cold temperatures, especially if the pool is covered and thus sunlight is limited.
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