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Thread: Getting wide fluctuations in CYA level

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    Join Date
    Jun 2015
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    Getting wide fluctuations in CYA level

    I am new to this and have only done about 10 CYA tests in my life starting about 2 weeks ago. However I am getting some huge swings in the level, I started out low, added CYA as per poolmath shot up to 40. I was happy and was going to use trichlor and when it got to 60 (I was hoping end of season) I would do a water exchange to lower for next season, a week later I am reading 50, so figured better stop trichlor that is bringing up way to fast, week has gone by I test yesterday I am reading 20. Any Ideas on what I am doing wrong? By the way the pool has not been used very much and I usually test CH & CC 2 x/day early AM & 6-7 in PM. overnight loss usually < .5 on FC, daytime loss about 2, this has really not fluctuated over the past week and a half since I came off slam, slam was only a few days because with knowledge from here and using pool store # till I got the test kit. I was dialed in close and my pool store testing was pretty accurate except for CYA could not read, they said it was because TA too low but TA was 70 so while it can be raised a little I did not think it a major problem.
    28,000 gals (20 x 40), IG, vinyl, Hayward Sand Filter, old Hayward
    Super pump (not sure of HP secondary to corrosion of label),

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    Texas Splash's Avatar
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    Re: Getting wide fluctuations in CYA level

    A note from a previous discussion: "Proper lighting is important for the CYA test. You want to test on a sunny day but keep the view tube in the shade. Taylor recommends standing in the sun with your back to the sun and the view tube in the shade of your body. Other than that, try it a number of times with a sample that you use over and over again, it should be good for at least five minutes, and see if you can get repeatable results. The CYA measurement is never exact. If you get results that are all within 10 of each other then you are doing well."

    Hope this helps give you ideas and reassurance. It can seem a bit finicky, but you'll get it. Good luck!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Mod Squad tim5055's Avatar
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    Re: Getting wide fluctuations in CYA level

    Quote Originally Posted by Texas Splash View Post
    A note from a previous discussion: "Proper lighting is important for the CYA test. You want to test on a sunny day but keep the view tube in the shade. Taylor recommends standing in the sun with your back to the sun and the view tube in the shade of your body. Other than that, try it a number of times with a sample that you use over and over again, it should be good for at least five minutes, and see if you can get repeatable results.
    Lighting is the key. Always try to test on days with similar lighting, preferably a nice sunny day.

    I always pour back and forth between the mixing bottle and the tube multiple times to get a good reliable reading each time I test.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Getting wide fluctuations in CYA level

    Thanks, the lighting may be the key, I will try as will as get a reference bottle with known CYA.
    28,000 gals (20 x 40), IG, vinyl, Hayward Sand Filter, old Hayward
    Super pump (not sure of HP secondary to corrosion of label),

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    BoDarville's Avatar
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    Jun 2012
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    Re: Getting wide fluctuations in CYA level

    More detailed instructions are also available here: Extended Test Kit Directions. Post # 8 deals with the CYA test.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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