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Thread: CYA is 100 FC should be 7 ???

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    CYA is 100 FC should be 7 ???

    My CYA is 100. Did I read correctly that my FC should be 7 ??? I though the FC should be 1.5 or so ??? Thank you.
    20X36 IG vinyl (18,000 gal), 3 sheer descents, Max-Flo 1.5hp VS 2300, Aquarite T15 SWG, C3030 filter, 250,000 BTU heater, Sharkvac XL (Hayward equip)

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    Mod Squad jblizzle's Avatar
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    Re: CYA is 100 FC should be 7 ???

    You read incorrectly, the FC should be 7 at MINIMUM ... likely need to target about 10ppm every day to keep it above 7ppm.
    See the FC/CYA Chart.
    Jason, TFP Moderator
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    Re: CYA is 100 FC should be 7 ???

    Someone will chime in and post a link for you with a chart but 7 does not sound too far off. And 100ppm of CYA is about 30 ppm over ideal for a SWG pool and about 50 ppm over ideal for a non SWG pool. If you do a drain/refill to get your cya to 50 you can half your FC number.
    30x20 vinyl IG, Hayward SD60 with Pentair Dynamo 340219 2HP pump, Compupool CPSC24 SWG, Hayward H200FDN heater. APC automatic pool cover.
    Central Illinois

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    Mod Squad jblizzle's Avatar
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    Re: CYA is 100 FC should be 7 ???

    To continue with what bdex said, your CYA is way too high and you really should replace about 50% of the water.

    I am also going to guess that you are using trichlor tablets and/or dichlor shock powders ... that would be the source of the CYA.

    How much Pool School have you read? Start with these:
    ABCs of Water Chemistry
    Recommended Pool Chemicals
    How to Chlorinate Your Pool
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: CYA is 100 FC should be 7 ???

    Yes JB. I'm using tablets. Only started in April with brand new pool. I'm still learning guys. I did read the topics above. The CYA would explain why I just had a blow up of Algae. Water has been crystal clear since April, until yesterday that is. SLAMMING pool now. Oh, also I have been using Calcium Hypochlorite Shock once a week. Thanks guys.
    20X36 IG vinyl (18,000 gal), 3 sheer descents, Max-Flo 1.5hp VS 2300, Aquarite T15 SWG, C3030 filter, 250,000 BTU heater, Sharkvac XL (Hayward equip)

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    MBG75's Avatar
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    Re: CYA is 100 FC should be 7 ???

    ImageUploadedByTapatalk1408151820.619586.jpg

    So your slamming the pool at FC of 39?
    25k IG vinyl SWG Haywood 4830de 1.5hp TF-100

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    CYA is 100 FC should be 7 ???

    How did you measure your CYA value?

    Most CYA tests top out at 100ppm and pool stores are notoriously bad at both measuring and reporting CYA. For example, my local pool store often would tell me my CYA was 99 and it was "OK". Actual value was over 150ppm and it certainly was NOT ok.

    If your CYA is over 100ppm, doing a SLAM is going to be difficult and expensive considering the amount of bleach you'll need to add to get to a shock level of FC. Chlorine consumption and dissipation also increases with increasing concentration of FC, so maintaining that shock level will require a lot of bleach as well.

    Can you post a full set of water chemistry values from a K-2006 or TF-100 test kit?



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    Re: CYA is 100 FC should be 7 ???

    To add to Sunny's post, perhaps try and dilute the water for the CYA test. A 1:1 dilution (pool water/distilled water) should allow you to get a reading of less than 100. Once you have that reading, just multiply by 2 to get the actual CYA.

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    Re: CYA is 100 FC should be 7 ???

    Quote Originally Posted by Donny View Post
    Oh, also I have been using Calcium Hypochlorite Shock once a week.
    Your calcium levels may be getting high as well. All sold forms of chlorine add byproducts the will build up to unacceptable levels if used exclusively. Start reading pool school and expect to be using liquid chlorine/bleach in the future or add a salt water generator. If your CYA is 100, you can keep the algae at bay by properly chlorinating. It will require a good test kit (to test high levels accurately) and some practice. My pools was about 120 when I started. It's a lot easier now that I'm down to 90. If you water is cheap enough, I'd replace it instead of dealing with high CYA. My part of the country is currently in an extreme drought. I also keep my pool open all year. I assume in NY, you'll be closing your pool before too long. So maybe you can just live with it until then. Still, you need to know how much over 100 you are. When we see 100 here we generally assume the test hit it's max and the actually value is higher.
    20,000 gal in-ground plaster pool with sand filter. Replastered recently. Mostly adding bleach and acid. CYA was high when I took over.

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