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Thread: Lower CYA?

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    JasonLion's Avatar
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    Lower CYA?

    Quote Originally Posted by twokidz
    This is my 1st time posting a message, so here's a brief history to bring you up to date...

    Four yrs ago we had a 26k gallon in ground pool installed w/ a heater. For the first four yrs I was under the impression that all I had to do was check the water weekly with the teststrips (which I did religiously) Ocassionally making slight adjustments with the help of the pool store. This year when they opened the pool we discovered that our heat exchanger had pin holes in it. I am told this was a result of bad water chemistry.

    I went right out and purchased the Leslie's Total Poolcare DPD test Kit. In researching a new pool heater I discovered your website and signed right up. Since I've been using the new test kit my total and free chlorine #'s are always 5ppm+ (outside the 5ppm max of this test kit) I just ordered the TF Test kits FAS/DPD Chlorine test.

    My #'s today (Sunday 8-2) are:

    Free CH 5+
    Total CH 5+
    PH 7.3
    Alk 90
    Calcuim H 280
    CY 100++

    My question is; once I get the new test kit should I let my chlorine #'s stay high if my CYA is always 100+ (based on the Chlorine/CYA chart) or should I lower my CYA and go for the #'s recommended on the site for vinyl pools?

    I should mention that to get mychlorine #'s @ the 5+ they are now, I sometimes have to turn off the chlorinator (3" dichlor) for days at a time. I live in the Northeast USA (Long Island) the water in the pool is clear. I hope I have explained this all correctly.

    Thank you for your help.

    18'x40' 26,000 gallon vinyl in ground
    Hayward Sand Filter (s244s) 62GPM 1 1/2 hp
    Jandy Lite heater (LJ325N)
    Polaris 380 Robot
    Hayward Automatic Chlorine Feeder
    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

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    reebok's Avatar
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    Re: Lower CYA?

    dichlor is adding cya, though I suspect you mean trichlor if it's a chlorine tab feeder (chlorinator) you're talking about. you need to stop adding cya now and you really need to drain some water, especially if you don't truly know your cya level. cya of 100+ requires a lot of chlorine to keep up with, which in turn makes your testing significantly longer, etc.
    you can use the dilution method if you would like for a bigger range on your FC test and CYA test, though you lose some accuracy. with the FC test you need distilled water, which you may or may not have. half pool water and half distilled water gets you a range of 10ppm. this is still mostly worthless with a cya of 100+. with the cya test you can use half pool water and half tap water, then multiply your result by 2.
    your numbers look mostly ok, the TA is a bit low for using chlorine tabs, but hopefully you won't be using them anymore.
    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

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    JasonLion's Avatar
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    Re: Lower CYA?

    I strongly recommend that you replace water to get CYA below 100, preferably down to around 50. As reebok already pointed out, both dichlor and trichlor add CYA, which is just making things worse.
    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

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    Re: Lower CYA?

    Thank You for the quick response.I am confused by what you mean when you say that a cya of 100+ will take a lot of chlorine to keep up with.I have to shut the chloinator off at times to keep the chlorine level down.Also you were right about the trichlor.Thanks Again

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    Re: Lower CYA?

    TC of 5 is not high for chlorine when you have 100 CYA. The proper sanitary range with CYA of 100 is 8 to 13 and your Target should be around 11. Shock level would be 25. If your CYA is higher than 100 then the chlorine range should be even higher.
    Buggs

    14,000 gallon, in ground, plaster, free form, play pool.
    Sta-Rite Max-E-Glass with a 1.5 hp Emerson motor
    WaterCo Micron High Rate sand filter S750 490 lb, 4883 sq ft - using ZeoBest
    In floor Polaris cleaning system
    Blue Diamond robot for those after storm days when I can't wait overnight for the in floor to clean it.

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    Re: Lower CYA?

    How much water would you recommend replacing in a 26000 gallon pool with 100+ cya, to get to around 50 cya......1/2?

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    frustratedpoolmom's Avatar
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    Re: Lower CYA?

    Depending on the pool's specific specs, draining more than 1/3 at a time could be harmful. You don't want to cause damage to the liner so in general we say 1/3, refill, recirculate, retest, repeat if necessary until the CYA is into range.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: Lower CYA?

    With an inground vinyl pool, the usual advice is to drain down to where you have at least 1' water left in the shallow end, or down to your local groundwater level, whichever is higher. You want to keep enough water in there to keep the liner in place, and you don't want the groundwater trying to make the pool "float."

    Let us know if your local water table is high, there are some other tricks you can do that will end up using more water but will avoid any potential damage to the pool.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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    Re: Lower CYA?

    Well I drained about 1/3 of my pool, leaving 1' in the shallow end.I refilled and let the filter run all night and my cya is now at 100 wich is a slight improvement. I am going to try it one more time and see what happens.Thanks for the advice

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