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Thread: Safe to swim w/ FC > 10ppm?

  1. Back To Top    #1

    Join Date
    Aug 2010
    Location
    San Jose, CA
    Posts
    12

    Safe to swim w/ FC > 10ppm?

    First time owning a pool this year, and it's been very educational! Thank you TFP Pool School!

    Short story:
    Do I understand this chart correctly... if the CYA level is 90 or above for a non-SWG pool, it's safe to swim with FC at 10ppm?
    pool-school/chlorine_cya_chart_shock

    Long story:
    Made the rookie mistake of using nothing but Trichlor tabs for the first 6 months. Over time, algae kept blooming and became harder to kill. After going to Pool School, I learned it was due to increasing CYA levels. I stopped using the tabs and switched to bleach. I elevated the FC > 10ppm for about week and finally got rid of the algae. Water is a nice clear blue now.

    I have not added any chlorine since the last shock treatment on 8/16. The pool gets a lot of sun during the day and it has been very warm and sunny here in San Jose CA. I do have a clear solar blanket on the water (don't know if that affects FC). But I'm surprised the FC has remained high for so long. I confess that I did not have a good test kit during the shock treatment, so I suspect I went overboard with the bleach / Cal Hypo to eliminate the algae.

    I just received my TF-100 XL kit today, but it was too dark for an accurate test. Instead I did a quick check with strips:
    TC 10 (strip cant test above 10)
    FC 10 (strip cant test above 10)
    TA 80
    PH 6.6
    TH 500

    My CYA is somewhere between 50 and 90 based on two tests from two local pool shops. I'll get my own reading tomorrow with the TF-100 kit.

    So, if my CYA is near 90, is it safe to swim with FC at 10 (assuming I increase my PH to the proper levels)?
    42,000 gallon, 24'x44' rectangle, inground plaster.
    Pool age 30+ years.
    Hayward C-4025 cartridge.
    Polaris 280.

  2. Back To Top    #2

    Join Date
    Apr 2010
    Location
    Buckeye, AZ 85326
    Posts
    618

    Re: Safe to swim w/ FC > 10ppm?

    Welcome to the site. You will not have any issues swimming in your water. Post up a full set of test results ASAP so the experts here can get you 100% dialed in.
    11,872 Gallon IG Shotcrete play pool
    Blue Granite Pebble Sheen finish
    Hayward SwimClear c4025, Navigator & Tristar 1.75hp pump
    2' Powerfall

  3. Back To Top    #3
    dmanb2b's Avatar
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    Apr 2009
    Location
    NY
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    3,728

    Re: Safe to swim w/ FC > 10ppm?

    If CYA is truly 90, then yes swimming in water with FC of 10-35 would be considered safe. Post the results with the TF100 1st so we can make sure you #'s are accurate. PH at 6.6 is too low.

    Welcome to TFP
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

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    JasonLion's Avatar
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    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Safe to swim w/ FC > 10ppm?

    How high FC can be and still be swimmable depends on your CYA level. Generally it is fine to swim when FC is below shock level for your CYA level. See the Chlorine / CYA Chart.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  5. Back To Top    #5

    Join Date
    Aug 2010
    Location
    San Jose, CA
    Posts
    12

    Re: Safe to swim w/ FC > 10ppm?

    Here are the results from the TF-100 kit:
    FC 9.5
    CC 1
    TC 10.5
    PH 7.2
    TA 90
    CH 530
    CYA 50

    FC of 9.5 is a bit high for CYA of 50, but is well below recommended shock level of 20. Should be OK to swim, right?

    I welcome any and all feedback.

    Thanks!
    42,000 gallon, 24'x44' rectangle, inground plaster.
    Pool age 30+ years.
    Hayward C-4025 cartridge.
    Polaris 280.

  6. Back To Top    #6
    dmanb2b's Avatar
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    Apr 2009
    Location
    NY
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    3,728

    Re: Safe to swim w/ FC > 10ppm?

    Ch is kind of high, but that's OK as long as you keep PH below 7.8 and that seems to be fine.

    My concern is not your FC #, that's fine for swimming with CYA at 50 but the CC of 1 is not. Perform the overnight FC loss test to confirm, but you'll need to shock to get the CC down to 0.5 or less.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

  7. Back To Top    #7

    Join Date
    Aug 2010
    Location
    San Jose, CA
    Posts
    12

    Re: Safe to swim w/ FC > 10ppm?

    High CH probably due to the Cal Hypo shock. I'll stick w/ bleach for now.

    OK, I'll check out my overnight FC loss and get the CC down.

    Thanks for your help.
    42,000 gallon, 24'x44' rectangle, inground plaster.
    Pool age 30+ years.
    Hayward C-4025 cartridge.
    Polaris 280.

  8. Back To Top    #8

    Join Date
    Aug 2010
    Location
    San Jose, CA
    Posts
    12

    Re: Safe to swim w/ FC > 10ppm?

    Overnight Test:
    FC night 8, morning 7.25
    CC night 0.5, morning 0.25

    I tested twice in the morning and averaged the two, which is why I have the ".25" granularity. Looks like the pool is OK... now if only the weather would warm up again.

    Thanks everyone!
    42,000 gallon, 24'x44' rectangle, inground plaster.
    Pool age 30+ years.
    Hayward C-4025 cartridge.
    Polaris 280.

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