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Thread: FC Level to maintain

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    FC Level to maintain

    Following the recommendations through Simple Pool app (and elsewhere) for my CYA of about 42, I need a minimum FC of 3, target of 5, and max of 7. I test FC daily or every other day.

    It is my understanding that I never want to get below FC of 3.0, or run the risk of algae to start growing. Over the last month, I have dropped as low as 2.5 twice.

    Is it best to try to maintain 5.0 with daily bleach addition, or is it ok to increase to 5 (or 7), and don't add until it reaches 3 or 3.5? At higher FC levels, I think I remember reading that the FC drop is greater, but I cannot find evidence of this statement right now.
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    Richard320's Avatar
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    Re: FC Level to maintain

    If you always test and dose at the same time each day, and you find yourself coming up short, then target a slightly higher FC. The rate of loss difference between 5.5 and 5 is negligible; the rate of loss difference between 15 and 5 is huge.

    It's safe to swim up to shock levels, so targeting a higher number isn't a big deal.
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    Mod Squad jblizzle's Avatar
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    Re: FC Level to maintain

    There is not really a max , keep it below shock level. The key is to always stay above the minimum ... target what you need to keep it above the minimum. But if you are losing more than 3ppm in a day, that could be a sign of problems.

    The CYA kinds sets a % of FC that will be lost to the sun each day. So if the FC is higher, for the same CYA, you will lose a little more.
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    Re: FC Level to maintain

    Quote Originally Posted by jblizzle
    There is not really a max , keep it below shock level. The key is to always stay above the minimum ... target what you need to keep it above the minimum. But if you are losing more than 3ppm in a day, that could be a sign of problems.

    The CYA kinds sets a % of FC that will be lost to the sun each day. So if the FC is higher, for the same CYA, you will lose a little more.
    Thanks for your replies. I am only loosing about 1 or 1.5ppm per day depending on usage. I will probably adjust my method to target 7 instead of 5, and add more at 4 or 4.5.

    Once all this rain stops, I will also have to recheck CYA. We have received over 10 inches of rain in the last week, so that is tending to decrease my CYA level.
    24' round above ground, 13500 gallons, vinyl liner, cartridge filter, Jandy Legacy 175,000 BTU heater, unused Zodiak Nature2 mineral sanitizer

    John 1:12 "But to all who did receive him, who believed in his name, he gave the right to become children of God"

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