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Thread: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool?

  1. #1
    Senior Member dino1956's Avatar
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    CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool?

    My CYA is at 122. Very High. And I'm not ready to Drain 60% of my Pool Water at this point in time.
    I'm no Longer Using the Chlorine Tabs, so I'm hoping my CYA doesn't get any higher.
    I have a couple of Pool Leaks in My Tiles That Cause It To Leak 1 Inch of Water in 3 Days.
    I'm hoping the combination of the Leak, Rain & Refilling will Lower CYA at least a little bit.
    My Question is, How much Bleach or Chlorine Will It Take To Shock My 28,000 Gallon Pool?
    Also, Can I Still Use The Pool Shock Granules in Packets?
    Thanks in advance.
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  2. #2
    Administrator JasonLion's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    I strongly recommend you replace water to get your CYA level down to something more reasonable. Fighting algae with CYA at 100+ is exceedingly difficult.

    One big problem is that there is no way to know if your CYA is really 122. None of the common tests are at all precise at levels above 90. Your CYA level could just as likely be 200 as 122.

    "The Pool Shock Granules" might be any of several chemicals. You really want to avoid using anything that contains dichlor, which like the tablets contains CYA. Products that contain cal-hypo are usable as long as your CH level isn't too high, though they are generally powers instead of granules.

    Everything else can be figured out using the Pool Calculator. See the link in my signature.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    TFP Admin. Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. #3
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    Thanks for the quick response.
    I have concerns about foundation & such. There are fine line cracks in concrete on Pool Deck.
    If I empty half the Water, is it safe? I would not want my pool to crumble into pieces.
    And how could I safely dispose of 15.000 Gallons of Water?
    The cost of the new Water would be about $200. I'm guessing. But that would be ok.
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  4. #4
    Administrator JasonLion's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    Unless your pool is in the middle of an obvious swamp you can always pump out 18" safely. If need be you can do that several times. This is a slightly less efficient use of water, i.e. uses more water, but otherwise works just fine. If you know how deep the ground water table is in your area you can pump down to that level without problems.

    The amount of water in a pool isn't really all that large compared to the amount of water that falls on your entire property in a heavy rain. There is almost invariably a storm drain, or other place where rain runoff accumulates that is safe to pump to.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  5. #5
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    What would be the best method to drain the water out?
    Obviously the Faster, the Better. Don't want to have too many days without my Pump Running.
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  6. #6
    Senior Member SkyKid's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    You could always use a garden hose to drain the water and add water with another garden hose
    That way you are changing water slowly
    Put your siphon hose on one end and the the other hose on the opposite end
    Not my idea
    I believe I read it here and it makes sense to me anyways
    14600gal, In-Ground Fiberglass, Haywood s244t Sand Filter, Jandy Apure35 SWG,
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  7. #7
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    It's a great idea. But in that scenario, how do I keep track of how much water was drained?
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  8. #8
    Senior Member harleysilo's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    You should match the fill rate with the drain rate using a bucket and a timer. Then you can multiply out the time into gallons exchanged. You could also use a big tarp to separate the water, lessening mixing, some people put a huge tarp all across the pool, fill water on top of tarp, draining water frOm underneath.
    18'x43' Sport Pool
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  9. #9
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    Interesting & helpful techniques. I like the tarp idea. Thanks!
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  10. #10

    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    Dino,

    I went through this whole process. Due to my infloor cleaner plumbing, the main pump will only drain 7" from my pool. So what I did was buy a 1/3 hp submersible pump (from harbor freight) with 1.5" outlet and a drain hose (had to get this from sears hardware store for some reason). This pump took 4.5"/hour out of my pool. My pool is about 38x18. I let it run for 3 hours (about 13"), then turned the hose on to refill, it takes about 9 hours to fill up. I did this 3 times as my CYA was near 200. My CYA is now somewhere around 30-60 (I can't read that darn test for nothing).

    Jason is right, with CYA that high, you will spend more money on chlorine than water trying to fix it. Plus, you will have to maintain a high level of FC after the shocking is complete.
    20,000gal, Gunite, Pebbletec, Chlorine, PCC2000 cleaner, StaRite S7M400 Cartridge Filter, MegaCatch Mosquito Trap

  11. #11
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    Yea I have no doubt you are all are right. Before this Forum, I knew nothing about CYA. And my Pool guy for the last 7 years never mentioned it. I'm waiting to get me test kit to test what the CYA is. My current Kit doesn't test for CYA. The reading I have is from an ACE Hardware Store & I don't trust it. I'm sure my luck, the CYA is actually over 200.
    I see a lot of discrepancies in running the CYA test. Why is it so hard to get a true number?
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  12. #12
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    If you test CYA with liquid reagent, you should be able to get + or - 10ppm which is certainly good enough for what we all need. Testing with ANYTHING else can be somewhat or even drastically unreliable.
    Dave S.
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  13. #13
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    Yea I'll wait for my Kit to give the real test! In the meantime, I lowered my PH a bit buy going by The Pool Calculator & adding almost 2 Quarts of Muriatic Acid. I tested with the old Test Kit.
    It's almost where it should be.
    I'm having a **** of a time with Pollen, Leaves, etc...I'm going to have to try out my first Manual Vacuum soon. The Polaris just won't get the small stuff.
    I'm taking Baby Steps here, I know.
    Tomorrow, just for the **** of it, I'm bringing a test sample to ACE Hardware to see how off their Computer really is. See if it says PH came down. I work next door to them, so nothing to lose.
    I'd like to thank each & every one of you that replied to my posts. I really do appreciate it. I no longer feel like a Deer in Headlights!
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  14. #14
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    One more thing. If I put Bleach, Liquid Chlorine & the Shock in the Packets in my Pool, will any of that raise my CYA?
    I'm done with the Chlorine Tabs. Just want to make sure I don't do something to make it worse.
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  15. #15
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    harleysilo,
    Like your idea of Fill Rate Matching Drain Rate.
    Since I have a Spa attached to my Pool 40 feet away from the Deep End, Couldn't I fill from the Spa end & Drain from the furthest part away of the pool's Deep End. Then the new Water would go in over the wall of the spa.
    Does that sound right? Or will that not work & I'll be losing the new Water?
    Thanks.
    Dino
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

  16. #16
    Senior Member
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    Quote Originally Posted by dino1956
    One more thing. If I put Bleach, Liquid Chlorine & the Shock in the Packets in my Pool, will any of that raise my CYA?
    I'm done with the Chlorine Tabs. Just want to make sure I don't do something to make it worse.
    Bleach and Liquid Chlorine are the same thing, Sodium Hypochlorite - just different % strengths.

    Shock in the packets may contain CYA - Dichlor - "dichloro-s-triazinetrione" is the active ingredient - contains CYA.

    There are other forms of packets labeled "shock" that are not Dichlor and do not contain CYA. MPS and Cal-hypo are two examples.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
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  17. #17
    Senior Member dino1956's Avatar
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    Re: CYA = 122 How Much Bleach To Shock a 28,000 Gallon Pool

    So basically if you go bleach or Liquid Chlorine, no CYA
    From them. Thanks.
    20' X 40' Rectangular Gunite Pool with Spa
    28,000 Gallons
    Sand Filter
    Rainbow Chlorinator
    Penair Pump
    Polaris 280

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