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Thread: Confusing why CYA is too high

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    Confusing why CYA is too high

    25,000 gal pool with SWG. During the winter I turn off the SWG and add a few pucks a month to the water via a floating dispenser. I have not added CYA to the pool over the last four years.

    I add about 1/2 gallon of acid a week to keep proper pH.

    In the summer, about every 7-10 days I add 3 bags of "sodium dichloro-s-triazinetrione" powder. (Yes I know you guys discourage powder shock, but it does work). I also add some phosphate lowering product (I know you hate that too) in the spring. Finally, I do add a small amount of bromine ("No-More problems") every few months. All of this will usually keep yellow algae out of my pool.

    So this week I tested the CYA level and it is greater than 100 !!! Tested it again, made sure it was mixed properly and got the same results. I am using the Taylor test kit where you add the mixture (7 ml pool water+7 ml of reagent) until you cannot see the black dot anymore.

    What is happening???
    35,000 gal pool, Pebble-Tec, Pentair VF pump, DE filter, Aqua Rite SWG, Pentair Minimax Heater in Southern California

  2. Back To Top    #2
    UN1017's Avatar
    Join Date
    May 2012
    Sacramento, CA

    Re: Confusing why CYA is too high

    It's really not too confusing. Remember, CYA is added to the pool either by stabilized chlorine products or CYA on its own. Each puck you use and every bag of "shock" (in your case, dichlor) adds to it.

    The only "shock" you should be using is bleach.

    Here some good info from Pool School.

    The bleach alternatives are not necessarily bad, as long as you know that the side effects are intentional on your part.
    15'x30' IG - Roman-style - 14K - Pebble Fina Classico
    Filter: Jandy CL460 Pump: Jandy Stealth SHPF1.5 SWG: Jandy AquaPure 1400 Cleaner: Jandy RayVac Test Kit: TF-100 w/SpeedStir

    Chlorine/CYA Chart----Extended Test Kit Directions----SLAM

  3. Back To Top    #3

    Re: Confusing why CYA is too high

    So the dichlor powdered shock has CYA in it? I did not know that.
    35,000 gal pool, Pebble-Tec, Pentair VF pump, DE filter, Aqua Rite SWG, Pentair Minimax Heater in Southern California

  4. Back To Top    #4

    Re: Confusing why CYA is too high

    3 bags of dichlor in your pool will add about 7.3 ppm of CYA. If you add 3 pounds per week, then in 14 weeks, your CYA will be raised by 100 ppm.

    Sodium bromide has turned your pool into a bromine pool, which will cause you to lose most of your chlorine as fast as it can be made by your SWG.

    You really need to read pool school as some of what you are doing is counterproductive and causing you problems.

    Used correctly, a SWG will pretty much do everything you need. If you need to add anything other than minor amounts of salt and CYA to make up for dilution, then you are not doing it the best possible way.
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  5. Back To Top    #5
    linen's Avatar
    Join Date
    Jul 2010
    Twin Cities, MN

    Re: Confusing why CYA is too high

    And each 3 inch puck (which are trichlor) assuming 8 oz adds 1.3 ppm cya.

    Take a look at this pool school article:
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  6. Back To Top    #6
    techguy's Avatar
    Join Date
    Jul 2010
    Antelope, CA

    Re: Confusing why CYA is too high

    If I understand it correctly, DiChlor and TriChlor Chlorine are "stabilized" into a solid form using a "Stabilizer"... or "conditioner"... or CYA

    Read this for more:
    -- Guy --
    10K gallons in 21' Round 52 inch wall Aqualeader AG, Hayward Power Flow LX 1.5 HP pump motor, Hayward Perflex EC50AC DE filter w/Cellulose, Wide mouth skimmer, 2013 new Diver Dan (craigslist) to replace the faded old Hayward AquaBug. TF-100

  7. Back To Top    #7

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Confusing why CYA is too high

    The following are chemical facts independent of concentration of product or of pool size:

    For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
    For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
    For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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