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Thread: Maintaining FC level

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    Maintaining FC level

    I know this will be a dumb question for some, but here 'tis.

    I have carefully monitored FC levels over the last several weeks, well, since discovering BBB awhile back. At around FC 4.0 I was getting some wide spread green algae growth to the point of shocking to 15ppm at my CYA level of 30.
    This evening I measured the FC level at 2.2 with CYA at 20 - I've added some water to the pool over the last several weeks.
    I've been trying to hold the FC at 5 - something tells me I can't get there with CYA that low. So, just about every evening I've added two 96 oz. bottles of 6% bleach to bring the level back up to 5 - according the the new and improved calculator.

    Adding bleach to the water everyday is common? Not that it's a problem, but what do you think? What needs adjusting other than maybe the CYA number?

    Thanks - and cheers !!!
    20x40 30,000 gal IG Liner, Pentair II Sand

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    duraleigh's Avatar
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    The chlorine usage sounds a little high....I can't remember the size of your pool or how much Sun you get but, for a normal pool around 20k that usage, while not horrific, is noticeably above average suggesting your chlorine is being consumed by organics.

    Naturally, the CYA @ 20ppm is contributing somewhat. Confirm by testing after sunset and then again in the AM (before the Sun hits the pool).
    Dave S. - Forum owner
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    JasonLion's Avatar
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    There are no dumb questions. Asking questions is how we learn.

    You need to get your CYA level up a little. CYA levels as low as 20 can be problematic. The test isn't all that percise, so a reading of 20 might mean 10 or 30. At a CYA of 10 I wouldn't be at all surprised if you lost 3/4, or more, of your FC over a sunny day.

    duraleigh's point is also important. If FC has gotten too low there is very likely at least some algae, even if not a full bloom, and it will take extra chlorine to get control of it.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Quote Originally Posted by duraleigh
    The chlorine usage sounds a little high....I can't remember the size of your pool or how much Sun you get but, for a normal pool around 20k that usage, while not horrific, is noticeably above average suggesting your chlorine is being consumed by organics.

    Naturally, the CYA @ 20ppm is contributing somewhat. Confirm by testing after sunset and then again in the AM (before the Sun hits the pool).
    It's a 30,000 gal and gets full sun.
    20x40 30,000 gal IG Liner, Pentair II Sand

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    If your pool gets full sun I would run the CYA closer to 50 ppm rather than 30 ppm.

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    Waterbear is right. I live in Phoenix and my pool is probably 98% of the time in full sun. I only get a little shade for a couple of hours. I find if I keep my CYA at 45-50, my chlorine levels are pretty darn stable.
    Buggs

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    Quote Originally Posted by Buggsw
    Waterbear is right. I live in Phoenix and my pool is probably 98% of the time in full sun. I only get a little shade for a couple of hours. I find if I keep my CYA at 45-50, my chlorine levels are pretty darn stable.
    I'll bump it up ... by the way the cya in the sock works great. Took less time to dissolve in the skimmer due to the constant water flow over it.

    Thanks for the info . . . cheers!
    20x40 30,000 gal IG Liner, Pentair II Sand

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