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Thread: Killing algae below shock levels?

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    Killing algae below shock levels?

    Within the last week or two, I've seen several pools that had no problems all summer, suddenly show significantly lower FC levels. This got me thinking about how this could happen.

    I'm thinking that these pools have had small amounts of algae growing all along, but in such small amounts that the SWG was able to maintain significant FC levels. There would have to be an equilibrium between the amount of FC generated and the amount consumed fighting algae. In many of these pools, the FC is up around 7 or 8 with CYA somewhere around 60. If the right conditions present themselves, the algae would have opportunity to shift the equilibrium, resulting in a sudden drop in FC and if not corrected, a full algae bloom.

    If my thinking is correct, I could expect the same pool to maintain the same FC levels at a lower SWG setting if there were no algae living in the pool, since none of the FC generated would be consumed maintaining the equilibrium with the algae.

    This would also mean that the shift in equilibrium could go the other way. If instead of conditions favoring the algae, they could favor the FC resulting in a slight shift allowing for greater retention of FC resulting in higher FC levels that should more rapidly kill algae.

    So this all seems reasonable to me, but it is all based on the assumption that algae can be killed below shock levels. So is it possible to kill algae without raising FC to shock levels?
    TreeFiter

    Pool Technician
    Saugerties, NY

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    Mod Squad jblizzle's Avatar
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    Re: Killing algae below shock levels?

    Yes, algae is killed below shock levels, you need to be at shock level to ensure that you are killing it faster than it can reproduce.

    It is very possible to hold a bloom at bay where you are constantly killing enough to keep the pool from going green. This usually presents by higher FC losses than normal.
    Jason, TFP Moderator
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    Re: Killing algae below shock levels?

    So my theory is plausible. I guess this is exactly why the OCLT is so important after SLAMming a pool.
    TreeFiter

    Pool Technician
    Saugerties, NY

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    Mod Squad jblizzle's Avatar
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    Re: Killing algae below shock levels?

    Yup.
    Jason, TFP Moderator
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    Re: Killing algae below shock levels?

    I'd love to find another way to measure chlorine demand without having to be there at sunrise and sunset. Just a thought; why wouldn't a water sample behave the same way as the water in the pool in terms of chlorine loss.
    TreeFiter

    Pool Technician
    Saugerties, NY

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    Mod Squad jblizzle's Avatar
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    Re: Killing algae below shock levels?

    The problem is the algae may not be in the sample you take ... it could be more localized somewhere else in the pool.
    Jason, TFP Moderator
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    Mod Squad tim5055's Avatar
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    Re: Killing algae below shock levels?

    Quote Originally Posted by jblizzle View Post
    The problem is the algae may not be in the sample you take ... it could be more localized somewhere else in the pool.
    like hiding in those light niches and the bottom or inside ladders.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Killing algae below shock levels?

    Or hiding in the float on your Polaris pool sweeper!
    28,000 IG, gunite, IntelliChlor IC40 SWG with SPA,
    Intellichlor/VS Pentair
    Norman, OK

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