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Thread: CYA and Dichlor

  1. Back To Top    #1

    CYA and Dichlor

    First off this is my second year with BBB and I couldn't be happier. Upon opening my pool I had test results of...

    ph- 7.5
    fc- 0
    cc- 0
    ta- 110
    ch-280
    cya- < 20

    I added the recommended amounts of bleach and in 1 day the pool was beautiful. However with CYA of less than 20 the chlorine has been sucked out pretty rapidly. I had some dichlor left over that of course I don't use anymore so I added 5- 1lb bags to raise the FC and the CYA. The question is, Do I wait a week to retest CYA? Or will using dichlor immediately raise the CYA by 11 (according to the calculator). I've been adding 121 0z. of 8.25% nightly and by the next day, it is gone. The one day I didn't do it, the water turned cloudy. Tested for CC's again today and still nothing.

    Thanks!
    28K IG Gunite, 60 sq. ft. Pentair DE Filter, 2.2hp WhisperFlo Pump, Polaris 3900 Vac in Baltimore, MD.

  2. Back To Top    #2
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: CYA and Dichlor

    No, when using dichlor you can retest CYA after 30 minutes with the pump running.

    If you are losing chlorine during the day, that is normal. But if you are losing chlorine overnight there is a problem.
    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

  3. Back To Top    #3
    Butterfly's Avatar
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    Re: CYA and Dichlor

    Yep, right away (or within 30 minutes to an hour anyway).

    But remember the CYA test is +/- 15 .
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    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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  4. Back To Top    #4

    Re: CYA and Dichlor

    Thanks guys.... Had to order some more reageant from Dave for the CYA test. I'll just keep adding bleach daily until it arrives and before I think about the doing the OCLT.
    28K IG Gunite, 60 sq. ft. Pentair DE Filter, 2.2hp WhisperFlo Pump, Polaris 3900 Vac in Baltimore, MD.

  5. Back To Top    #5

    Join Date
    Jun 2012
    Location
    Louisville, KY
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    266

    Re: CYA and Dichlor

    You have zero FC in your pool so letting it dip that low is inviting something to grow. The OCLT is a good way to tell if you need to shock or not or if you've got something growing in your pool. I'd perform one as soon as possible given your water turned cloudy when you let your chlorine drop.

    It doesn't take long, it can happen during one day for algae to take hold even if there are no visible signs.

    Dose in the evening to target/shock level, test FC, test FC in the morning before sun hits the pool. Doing a OCLT is a sure fire way to see if you've got problems other than sun loss of chlorine.

    Nip it in the bud.

    Using poolcalculator at 10% bleach for your volume with 121 oz only raises FC by 3.4. You're using 8.25. You're not able to keep up.
    18x36 inground vinyl lined, Hayward sand filter and tablet chrolinator, approx 18k gallon

  6. Back To Top    #6

    Re: CYA and Dichlor

    Raised FC to 5.5 and will check in the morning to see if I need to shock. Why does it seem to rain every time I try to do this? Thanks!
    28K IG Gunite, 60 sq. ft. Pentair DE Filter, 2.2hp WhisperFlo Pump, Polaris 3900 Vac in Baltimore, MD.

  7. Back To Top    #7

    Re: CYA and Dichlor

    OCLT held steady at 5.5 this morning. Tested again tonight and am down to 1 FC which will need 127 oz. of 8.25% to bump back up to a target of 4 FC. When my CYA reagent arrives, I'll test again and try to get my CYA up to around 40 with the dichlor.
    28K IG Gunite, 60 sq. ft. Pentair DE Filter, 2.2hp WhisperFlo Pump, Polaris 3900 Vac in Baltimore, MD.

  8. Back To Top    #8

    Join Date
    Jun 2012
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    266

    Re: CYA and Dichlor

    Quote Originally Posted by Jerry Lee
    OCLT held steady at 5.5 this morning. Tested again tonight and am down to 1 FC which will need 127 oz. of 8.25% to bump back up to a target of 4 FC. When my CYA reagent arrives, I'll test again and try to get my CYA up to around 40 with the dichlor.
    Sounds like a plan and it is indeed the sun using up your FC due to low CYA. You can overshoot your target FC by some to compensate for the loss to ensure you never drop below minimum.

    You know how to use poolcalculator to see the effect of the dichlor you're adding in terms of FC and CYA? Sounds like you've got a handle on things and have the dichlor on hand you can "get rid of effectively" to reach your goal.

    -edit-
    nevermind, you're rocking the poolcalculator and understanding the impact
    18x36 inground vinyl lined, Hayward sand filter and tablet chrolinator, approx 18k gallon

  9. Back To Top    #9

    Re: CYA and Dichlor

    Thanks again for the input!
    28K IG Gunite, 60 sq. ft. Pentair DE Filter, 2.2hp WhisperFlo Pump, Polaris 3900 Vac in Baltimore, MD.

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