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Thread: plaster preparation, small spots

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    plaster preparation, small spots

    So,

    We recently remodeled, and the contractor (who also has a CA c-53 pool license) was charged with replumbing and replastering the pool. He was subsequently fired for problems other than the pool, but this left us with a pool that was unfinished.

    The pool was left basically ready for plaster, with plumbing in place, and old plaster gouged out. There the pool sat for over two years, becoming a black swamp populated by mosquito fish and plants provided gratis by county vector control (one of the few government entities Ive ever actually enjoyed working with.)

    Fast forward to recent times. I hired a new pool guy with >35 years in the business and high praise from customers. He pumped the swamp, installed fittings, and replastered the pool. The pool has been full for about 5 weeks now.

    Im doing maintenance myself, and recently noticed that there are some small black spots here and there that dont vacuum up. I have been able to dislodge most with the nylon pool brush, but a few persist. Otherwise the chemistry is under control (starting about 2 weeks in,) and the plaster looks pretty good.

    Two questions:
    [list=2:2xs1otz6]1) Can black algae for that quickly, or is this more likely dirt?
    2) I know this is not related, and possibly way too paranoid, but should the contractor have bleached the shell (remember, he had to pump out a shallow black swamp) before replastering to stop any growth that might start from the back side of the plaster, or does the lye in the fresh plaster take care of that?[/list:2xs1otz6]

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    Mod Squad Bama Rambler's Avatar
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    Re: plaster preparation, small spots

    The first thing to do is post a set of test results.
    Black algae can certainly form in 5 weeks. How have you been chlorinating your pool?
    If you keep the FC where it should be according to your CYA you won't get any kind of algae.
    Dave J. TFP Moderator
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    Re: plaster preparation, small spots

    Chlorine is liquid 12.5%, just started adding tablet. FC has varied a bit on the low side, but usually only for a day or so. FC was zero for first 2 weeks, as per instruction from plaster guy. He didn't want me to add chlorine until the ph was brought down, gradually, which took about 2 weeks.

    Right now? CYA 40, FC 2.0, PH 7.6

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    Mod Squad Bama Rambler's Avatar
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    Re: plaster preparation, small spots

    Your FC is way too low for a CYA of 40 ppm. Going without chlorine for 2 weeks is a sure recipe for algae.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Mod Squad jblizzle's Avatar
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    Re: plaster preparation, small spots

    Can you scrap one of the black spots off and smear it on a white piece of paper ... would be a dark green if it is black algae.
    Jason, TFP Moderator
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    Re: plaster preparation, small spots

    Have not seen any other evidence of algae, however. I'll try getting sample/smear and get back . . .
    Never a greenish cast. Can black grow without seeing signs of green?

    Pool store told me that zero chlorine was bad also, when I started pool, but plaster guy said they were wrong . . .

    Store now thinks FC 2-3 is fine! Lots of conflicting info . . .

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    Mod Squad jblizzle's Avatar
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    Re: plaster preparation, small spots

    Stick with the info you get here and you will be fine ... and have more money in your pocket.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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