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Thread: Perfect results, but bad method..

  1. Back To Top    #1

    Join Date
    Jul 2007
    Location
    Florida
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    64

    Perfect results, but bad method..

    New member here. Wish I learned about BBB few weeks ago.

    22000gal IGP, PebbleTec surfacing, cartridge filter, 8ft deep end.

    Color was greenish/cloudy for greater part of a year. Got fed up and decided to shock the **** out of it after reading about breakpoint chlorination. Did a rough test at local pool store first: FC=1, pH=7.2, TA=100, CH=240, CYA=60, TDS=500. Not knowing about CYA side effects, decided to dump ten 1lb. dichlor bags I had sitting around. Reasoning at the time was since dichlor was close to pH neutral, might as well shock with that so I dont' have to mess with pH balance.

    Chemical chart said 1lb/6700gal of dichlor results in 10ppm FC increase. So dumping ten bags shot my FC level to around 30+. After 2 days with pump running 24/7, pool was blue as can be, cystal clear everywhere. At 8ft deep, I could literally count individual pebbles on the surfacing. This is great!... or so I thought...

    Ordered TF kit and arrives sometime this week. But pool store tests now read FC=5+, pH=7.2, TA=110, CH=375, TDS= 600, CYA=100. It's not until I learned about CYA sources that I started kicking myself Only consolation is that the pool loooks perfect, at least for now. For all I know, CYA is well above 100.

    If I start using strictly bleach, will CYA at least slowly dissipate on its own given enough time?
    22,000 gal in-ground, 3-8ft
    Cartridge filter
    Pebble Tec resurfaced
    Polaris 360

  2. Back To Top    #2
    CYA goes away through splashout and backwashing, and if you need to drain due to rain. Some people have their CYA go down over the winter (with pool closed) but not everyone.

    CYA will not evaporate or be destroyed by anything you normally use in your pool.

    With your kit, you are well on your way to having a TFP!

    Welcome, if I have not said it before!

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, CYA-Chlorine Chart
    "Shock" is a process, not a product!

  3. Back To Top    #3

    Join Date
    May 2007
    Location
    Houston, Texas, USA
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    148
    rimshaker,
    Cya can be reduced via dilution (adding fill water, rain, etc). However, since you have a cartridge filter and don't have to backwash, the dilution will take quite a long time. You can maintain an algae free pool even with very high cya levels, you just have to maintain chlorine according to the cya. One big drawback of very high cya is that it takes extremely large amounts of chlorine if/when the need arises to shock. At 100 cya you would need to maintain 11.5 ppm free chlorine to prevent algae. But as you said, your cya could be even higher.
    Poor Man's Pool
    Doughboy 18 ft round above ground
    7600 gal with center drain
    Pentair sand filter, 1 HP pump
    50 ppm borates
    "I know just enough to be dangerous"
    Pool Calc Ver 1.41 (Excel)

  4. Back To Top    #4
    Rimshaker, you can either take out water and add fresh to lower CYA, or live with it.

    For a CYA of 100, your target FC is 11.5% or 11.5 ppm. Minimum FC would be 7.5% or 7.5 ppm.

    If you use bleach to keep you at these levels, your water should stay clear. Takes a bit to bump it up the first time, but once you are there to maintain it should only take the same amount added daily as it would have at lower CYA levels.

    One downside to running higher levels of FC is that the standard OT test is useless. You'll need a good FAS/DPD kit to allow you to get accurate readings in the range you'll need your FC. You can get this kit from Dave

  5. Back To Top    #5
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,887
    CYA only goes down from removing water and sometimes over the winter if you let the pool turn into a green swamp for a couple of months. Since you don't backwash with a cartridge filter I wouldn't expect it to go down significantly till winter, if then (unless you have rain like Texas has had recently).

    10 lbs of dichlor would add about 27 ppm of CYA to 22,000 gallons. Given that the CYA test has some variability, you are hopefully pretty close to a CYA of 100 now, but with pool store testing it is hard to be sure of anything. The problem is that the standard CYA test can't distinguish a level of 100 from a level of 200 or 300, they will often all read as 100. If the original test showing 60 was low for some reason you could be anywhere over 100.

    I suggest you replace some water soon and try to get CYA below 100. Hopefully it won't take too much. If your fill water has problems of it's own (metals, high alkalinity, etc) there are ways to manage high CYA levels, but they get to be a real drag with CYA at 100 or higher. For example you should keep FC at at least 8, and hopefully higher, until you get the CYA down. Yet testing for that level of chlorine is going to require the FAS-DPD test from the TF Test Kit, not something your pool store appears to have.

    By the by, dichlor is quite acidic in the long run.
    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

  6. Back To Top    #6

    Join Date
    Jul 2007
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    Florida
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    Since I have to maintain a higher FC level at all times (8+) due to high CYA, does this further inhibit new algae growth?... better than say having low CYA and FC around 2-4.

    I would think new algae would have a tough time establishing at constant FC levels above 5. If this is true, maybe a higher CYA is a small blessing in disguise?
    22,000 gal in-ground, 3-8ft
    Cartridge filter
    Pebble Tec resurfaced
    Polaris 360

  7. Back To Top    #7
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
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    37,887
    No, it doesn't work that way. You need the higher FC level to get the same protection you had at a lower FC level with lower CYA. The one improvement is that less chlorine will be lost to sunlight. Everything else gets more and more difficult at higher CYA levels.
    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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