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Thread: CYA question

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    cood60's Avatar
    Join Date
    Jan 2012
    Virginia Beach

    CYA question

    OK, this is strange. Last fall, in November, my CYA was at 40 ish
    The only chems added through the winter is bleach to keep FC at around 3 ppm
    I did not check again til a week ago. I had assumed it would be very much lower than 40 because throughout the winter I have replaced 16 to 20 inches of water due to lots of rain and some snow. About a week before checking (a week or so ago) I had added about 3 lbs of dry CYA using the sock meathod. Had also put some cellulose fiber in the the skimmers as a filter aid. To my surprise, the CYA level is at 80. I thought nothing but Conditioner would raise CYA and certainly 3 measly lbs in a 26,000 gallon pool would not raise it this much. Any idea how this could happen?
    The Bleach I have been buying is some new stuff that is concentrated so it says it is "equivalent to 181 oz of the normal jugs. It seems it is all that is available in my area.
    22'x40' IG, Freeform, 26K gal, Vinyl liner pool(2011), three returns plus two step jets, one slide, two skimmers, two LED lights, Stamped Concrete with Aqua PL-Plus Automation panel, Pentair Intelliflo VS, Hayward Pro Series High Rate Sand Filter 500lb, Hayward Turbo Cell T-Cell 15 (SWG) , Dolphin Robotic Pool Vac, Hayward Heat Pump.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: CYA question

    That is unusual, though your results (just barely) agree within the precision of the test. Adding 3 lbs of stabilizer should have raised CYA by 15 and the error on the test is around +-15, which means the readings can differ by 45 and still agree within the precision of the test. Though that is assuming the water replacement had no effect.

    Cold water will occasionally give a false low reading on the CYA test if you don't let the sample warm up to room temperature first. And the test can read higher than actual if you try to read it indoors. It is designed to be read in indirect full sunlight.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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