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Thread: Black Algae in Vinyl Liner

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    Black Algae in Vinyl Liner

    Hi! I have a vinyl pool that appears to be showing signs of black algae, I have read some topics relating to black algae but it seems most of the cases involve a gunite pool. Is my best option still to shock and brush or are the soft bristles of the vinyl liner brush not going to be effective?

    Thanks!
    ASP Pool and Spa of Asheville

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    Melt In The Sun's Avatar
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    Re: Black Algae in Vinyl Liner

    ASP, can you post some test results? Black algae is not a common problem in vinyl pools, since it can't dig itself into the surface like it can with plaster. Stains from organic material can be mistaken for black algae, and seem to be common in under-chlorinated vinyl pool.
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    Re: Black Algae in Vinyl Liner

    I have a taylor k-2005 kit

    ph-7.4
    tc- 2.0
    fc-2.0
    cc- 0.0
    cya - <30
    alk-50
    calcium hardness- 240
    ASP Pool and Spa of Asheville

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    Re: Black Algae in Vinyl Liner

    I think we need pictures, very unusual as stated

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    Re: Black Algae in Vinyl Liner


    ASP Pool and Spa of Asheville

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    Re: Black Algae in Vinyl Liner

    it has been spreading up the side of the wall in the deep end
    ASP Pool and Spa of Asheville

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    Mod Squad Bama Rambler's Avatar
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    Re: Black Algae in Vinyl Liner

    That doesn't look like black algae to me. I however, don't have a lot of experience with black algae. What happens if you hold a chlorine puck on it?

    It looks like a product of poor circulation in those spots. Raise the FC level and a good brushing should clear it up.

    What's the normal means of chlorination?
    Are you fairly confident of that CYA number?
    Dave J. TFP Moderator
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    Re: Black Algae in Vinyl Liner

    The normal means of chlorination is a floater with tri-chlor sticks and dumping granular chlorine in the pool. But every week when I return to the pool the chlorine is down to .5ppm or less. For that reason I feel confident that the CYA number is correct.
    ASP Pool and Spa of Asheville

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    Mod Squad Bama Rambler's Avatar
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    Re: Black Algae in Vinyl Liner

    That makes me suspect the CYA number even more.

    If you're seeing an FC of .5 or less those stains are most likely organic.

    Double check the CYA number and run an OCLT (overnight chlorine loss test) to determine if it's organics to the extent of needing to shock (I'd probably shock it anyway). Then keep the FC at the target level for the CYA.
    Dave J. TFP Moderator
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