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Thread: Can my FC really be that low?

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    Can my FC really be that low?

    Ok, I'm having an algae issue. It's my fault. I let things go too long and didn't stay on top of it. So, i'm trying to attack it today.

    I put 2 96oz jugs of bleach in today at 11:30. I just tested again (3 hours later) and it says my FC is 1! How can that be?

    I'm using a Taylor 2006 kit. Should I just keep adding a bunch more bleach. My CYA is high, so I obviously need a LOT more than that.

    Should I add several bottles at once?
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

  2. Back To Top    #2
    JasonLion's Avatar
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    Re: Can my FC really be that low?

    Just how high is your CYA level? It is critical to know your CYA level, and then add enough chlorine to get to shock level based on your CYA level, see this chart.

    You didn't add anywhere near enough bleach. 2 96oz jugs will raise your FC level by about 5. If your CYA level is say 60, you need to get the FC level up to about 20, and keep it there by adding more bleach regularly, to be effective. See this article for more information on shocking.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Can my FC really be that low?

    How can that be?
    Two things consume chlorine......Sunlight and organics (algae) in your pool.

    The algae has probably consumed the bulk of it but, if you have no CYA in the pool, sunlight will get the rest.

    It would be very helpful if you posted a complete set of test results and we'll help you get your pool back crystal clear.
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    Re: Can my FC really be that low?

    Thanks, I guess I do need a lot more bleach. My CYA is about 80 I think.

    I'll do the shock process now. Guess I need a trip to get more bleach!

    I'll try to get a full set of results soon. Thanks for the help.
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

  5. Back To Top    #5

    shock questions

    Merged posts. Please keep all q's concerning clearing your pool in this thread so that we have the history. Butterfly

    Ok, I get how to shock. I need to bring FC up to shock level and keep it there till the water clears. How long is that on average. I'm trying to determine how much bleach to get. I can calculate how much to bring it to shock, but how much am I going to need to maintain shock until it clears? Like a bottle a day? A few ounces a day?

    And how often do I need to check FC to determine if it's staying at shock level?
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

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    Re: Can my FC really be that low?

    Ok, here's my results

    FC = 7 (I've added more bleach since that reading of 1)
    PH = 7.4
    TA = 130
    CYA = 70-80 (I'm gonna go with 80 to be on the safe side).

    So, I need to bring FC up to 31. I posted another related question in the algae section, but I'll ask it again here. How much bleach will I need to KEEP it at shock level? I'm trying to determine how much more to get. And, how often do I need to check to see that it's staying at shock?

    Will I be adding bottles per day or ounces per day to keep it at shock?
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

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    How much would a store bought bag of "shock" raise FC?

    Merged for history. Butterfly

    The subject pretty much says it all. I have a few of these left over and was wondering if I could use them up since I need to shock for algae reasons.

    But I don't know how many to add. I know I need 2 bags per dose, but I don't know what that will raise FC.
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

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    Re: How much would a store bought bag of "shock" raise FC?

    Quote Originally Posted by Kathy3232
    Merged for history. Butterfly

    The subject pretty much says it all. I have a few of these left over and was wondering if I could use them up since I need to shock for algae reasons.

    But I don't know how many to add. I know I need 2 bags per dose, but I don't know what that will raise FC.
    That depends on exactly what is in the bag. If it is cal-hypo, then it adds Calcium which you may be low on or be too high on -- adding that could create a problem IF your calcium is way too high already. If it is dichlor or trichlor then it adds CYA which you really do not need any more of now but depending on how large your pool is and exactly what that means for you pool, it might be OK in a pinch.

    So, look at the contents of the bag and then go to the pool calculator and enter the size of your pool and any other info you have on the pool chemistry and such. Go to the bottom and see where it says Effects of Adding Chemicals.... see what that tells you about the CYA those bags will add to the pool or the calcium it will add. Then on the Suggested FC Level part, see what that change in CYA might do to the chlorine level you need to reach and maintain.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    reebok's Avatar
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    Re: Can my FC really be that low?

    I'd like to emphasize what anonapersona has said. if you want to use those bags of "shock" (ugh, misnomer) you need to know what they add. look on the ingredients. if it adds CYA do not use them. the last thing you need is a higher cya when you're already at 80.
    no one can tell you how much bleach, but you can see how much it took in a few hours today. so you can be sure it's going to be more than a few ounces.
    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

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    Re: Can my FC really be that low?

    It takes a very, very large amount of bleach to properly shock a pool and cleaqr it of algae, which you have.

    I would purchase 20+ of the very large jugs of Clorox for starters. Any that's left over after you successfully shock cam simply be added to the pool as your chlorine continues to diminish at much, much slower rates.
    Dave S. - Forum owner
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  11. Back To Top    #11

    shock level - Pool calc. vs. FC/CYA chart

    Merged for history. Butterfly

    When I enter my info. in the calculator. It tells me shock level is 21. However, on the Chlorine/CYA chart, it tells me shock level is 31. Which one is right?

    I've been going my 31, but it would save me a heck of a lot of bleach if I only needed to go to 21.
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

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    reebok's Avatar
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    Re: shock level - Pool calc. vs. FC/CYA chart

    the higher you go the faster it will work.
    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

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    Re: shock level - Pool calc. vs. FC/CYA chart

    What is your CYA level?
    I consider myself very lucky I found this site before the pool store found me-pool owner since Nov 2008- Stunningly clear 17,000 gal fiberglass pool, thanks to this site, installed in 1982-24" 3.1sq. ft sta-rite sand filter, 1 hp - 2 speed wisperflo pump-WFDS-4

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    reebok's Avatar
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    Re: shock level - Pool calc. vs. FC/CYA chart

    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

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    Butterfly's Avatar
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    Re: Can my FC really be that low?

    Hi Kathy,

    Please check your private messages.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    Re: Can my FC really be that low?

    but it would save me a heck of a lot of bleach if I only needed to go to 21.
    Not really. There is a certain amount of impurities in your water that take a certain amopunt of chlorine to get out.

    You can dabble the chlorine in there and it will take a lot more as you don't kill the impuritites (algae) or you can dose it up high enough so that there is always pleanty of available chlorine to kill it all completely.

    Most of the time you will consume far less bleach by dosing heavily (but not excessively) and holding it up high.

    When play pattycake with algae, it will play along for days and days. When you hit it with a sledgehammer, it will be removed from your pool.
    Dave S. - Forum owner
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    Re: Can my FC really be that low?

    Quote Originally Posted by Butterfly
    Hi Kathy,

    Please check your private messages.
    Thanks, I understand that your merging all these questions. But I like to post new ones when it's a new subject that I think my be helpful to someone else.

    Not to mention, they don't always get answered because people see the title and think "I already answered that" without realizing there was a new question.

    Thanks
    Kathy
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

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    frustratedpoolmom's Avatar
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    Re: Can my FC really be that low?

    Kathy,

    It's important for consistency to keep them all on one thread. The Mods and contributors read hundreds of posts a day, it's simply too confusing to have a new thread started every time there is a question, and many times new users think the issues are not related, when in fact, they are.

    Please keep the posts all on one thread.
    Helpful links: Pool School; CYA/Chlorine Chart
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    Re: Can my FC really be that low?

    Not to mention, they don't always get answered because people see the title and think "I already answered that" without realizing there was a new question.
    Nope. When we see new posts to a thread, it's revisited. Having one thread tells your story and helps everyone keep your issues straight. Trust us, you are much better off under one thread.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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  20. Back To Top    #20

    Is the Algae dead?

    Merged for history. Please keep all questions concerning clearing your pool in this thread. Butterfly

    Ok. I've been shocking with bleach and the pool is looking a lot better. The water is clear, but there is still "stuff" on the bottom where it's settled. Maybe there's poor circulation etc. How do I get that stuff out? I've been vaccuming and brushing etc. Will it just take time?

    BTW: the "stuff" is a yellowish brown color and mixes into the water as soon as I brush it. Then the water gets cloudy. Is this dead algae? Or is the algae still alive?

    **Up until today, I'd brush the steps and then later they'd be covered again. Today, they steps stayed clean overnight.

    I haven't tried to do the overnight test yet.
    27' round AG, sand, Ohio, well water, 19,000 gallons approx., New owners to the pool.

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