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Thread: Inconsistent CYA readings

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    Inconsistent CYA readings

    Hi everyone... I'm a new pool owner. I recently purchased a house with a pool and I have no idea what I am doing. I just received my K-2006 test kit but I am not sure if I am getting correct CYA numbers. Every other test were pretty consistent between my results, Leslie's pool, and the aquacheck strips. I'm not sure which results to use, mine or Leslie's.

    Over the weekend, I went to the local Leslie's to test my water and here is what I got on 4/1:
    FAC: 4
    TAC: 4
    CH: 300
    CYA: 60
    TA: 80
    pH: 7.5
    TDS: 1400
    Pho: 100

    Results with Aquacheck strips on 4/1:
    TH: between 250-500
    TC: between 5-10
    FC: 5
    pH: between 7.2-7.8
    TA: 80
    CYA: between 50-100

    My own test results on 4/2 after adding roughly 170oz of 8.25% bleach on 4/1.
    FC: 7.6
    CC: .4
    pH: 7.6
    TA: 80
    CH: 320
    CYA: 120 1:1 diluted (Aqaucheck strips showed less than 100 CYA)

    My results today 4/3:
    FC: 5.5
    CC: .5
    pH: 7.5
    TA: 80
    CH: 330
    CYA: 90
    ~38,000 Gallon In-Ground Plaster | Sta-Rite Intellipro 2 VST | Pentair CCP420 Filter | Polaris 360

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    Mod Squad pooldv's Avatar
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    Re: Inconsistent CYA readings

    Welcome to TFP!

    We will always trust your K-2006 or TF-100 test results, you should too. Toss the test strips in the trash and stay out of the pool store for water tests.

    More detailed test instructions here, Pool School - Extended Test Kit Directions
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    Re: Inconsistent CYA readings

    Thanks pooldv! I'll have to read the directions and try again.
    ~38,000 Gallon In-Ground Plaster | Sta-Rite Intellipro 2 VST | Pentair CCP420 Filter | Polaris 360

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    domct203's Avatar
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    Re: Inconsistent CYA readings

    Quote Originally Posted by DaytonaMax View Post
    Thanks pooldv! I'll have to read the directions and try again.
    Welcome to TFP!

    Are you doing the CYA test outdoors on a bright sunny day, with your back to the sun?
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    Re: Inconsistent CYA readings

    I did it indoors. Anything special that I would need to do? I haven't had a chance to read the instructions from the link yet.
    ~38,000 Gallon In-Ground Plaster | Sta-Rite Intellipro 2 VST | Pentair CCP420 Filter | Polaris 360

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    Patrick_B's Avatar
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    Re: Inconsistent CYA readings

    Quote Originally Posted by DaytonaMax View Post
    I did it indoors. Anything special that I would need to do? I haven't had a chance to read the instructions from the link yet.
    The kit instructions should tell you all you need to know, bright light at your back, outside.
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    dsmith99's Avatar
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    Re: Inconsistent CYA readings

    After your sample and reagent is mixed up you can run the test multiple times if you need to, just pour the contents of your tube back into the sample bottle and run the test again.

    This way you can try again to see if your result changes, view it under different lighting or you can even have someone else give it a try and see what they get.
    AGP 24' x 54" approx 14000 gal Full sun all day, Hayward 1.5 HP and EC50 D.E. filter
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    Re: Inconsistent CYA readings

    Thanks everyone. I'll have to try again later today.
    ~38,000 Gallon In-Ground Plaster | Sta-Rite Intellipro 2 VST | Pentair CCP420 Filter | Polaris 360

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    Divin Dave's Avatar
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    Re: Inconsistent CYA readings

    Also, to add, .... the water needs to be at room temp or above when testing for CYA. If the water is below 70 ish, bring it inside and let it warm up before testing.

    When testing CYA, the light conditions are very important. Always test outdoors in a sunny spot with your back turned to the sun. Also, when holding the test tube, hold it with only 1 finger and your thumb. Holding it with multiple fingers restricts the light from shining in through the side of the test tube and giving you an accurate result.

    Also hold the test tube at waist level when adding the solution and viewing the black dot.

    The measurement accuracy of this test is about +/- 10 ppm,
    Divin Dave,
    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
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    Re: Inconsistent CYA readings

    's about CYA testing.

    I try to test my CYA when the sun is at it's meridian ~ an hour or so (testing only on clear days) on the day I test, to test when sunlight is at or close to its maximum level.
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
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    Inconsistent CYA readings

    So I tested the CYA again today. I got a reading of 70. Thanks again everyone for all the help!


    ~38,000 Gallon In-Ground Plaster | Sta-Rite Intellipro 2 VST | Pentair CCP420 Filter | Polaris 360

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    FLPoolDIY's Avatar
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    Re: Inconsistent CYA readings

    I've done the CYA test multiple ways and typically have the same result.

    How I've done my test:
    1. Indoors held test tube at waist level and filled while glancing at black dot until no longer visible
    2. Indoors filling to each line and viewing at waist level until black dot is no longer visable.
    3. Placed tube on counter on a white piece of paper and filled to each line until the black dot was no longer visible
    4. Outside as defined on the instructions

    I've done all four with the same sample and had the same result. I think the key is to have bright enough lighting/sun for the test to be valid.

    As an added sense of accuracy I've used my ColorQ digital tester for CYA and its been within 10 ppm of what I visually identified with the test tube.

    When I first started doing this test it would drive me nuts 🥜 looking for the black dot to disappear.

    My neighbors were always curious what I was mixing in the little tube when I first started testing outside.
    FL, 15K gal (15x30 rectangle beach entry), IG Plaster, 2010, 1 skimmer, 4 returns, ecostar VSP, Pro Clean (PCCF-125) cartridge filter, IC20 SWG, Hayward Navigator floor suction cleaner, solar heat, waterfall, 2 lion head spouts, 1hp pump, TF-100 w/SpeedStir

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