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Thread: What happened to my CYA?

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    Join Date
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    What happened to my CYA?

    It seems like I have been going through alot of Chlorine as of late, and I finally got time to test my CYA tonight, and it is less than 20, I can see the dot clearly with the tube full. The beginning of the year, it was 30. I have been attacking my TA through aeration, could that have made the CYA go away? I added 1 1/2 pounds tonight, which should bring it back up to around 35. I have an 18 foot round, 7600 gallon pool.

    No Combined Chlorines.
    Cl is 5
    ph is 7.5
    TA is 120
    CYA is <20
    steve

    Above Ground / 18' Round / Vinyl Liner / Sand Filter / 100K Gas Heater / Salt Added / No Nature2

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    Hmmm, have you been refilling frequently from backwashing, evaporation or any leaking in your system?
    Buggs

    14,000 gallon, in ground, plaster, free form, play pool.
    Sta-Rite Max-E-Glass with a 1.5 hp Emerson motor
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    mbar's Avatar
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    I know that cya can b e eaten by organics - I usually lose my cya over the winter. If you haven't been adding a lot of water, maybe it is time to shock - have you tested if the chlorine is holding overnight? In the beginning of the year it took me a couple of weeks for my chlorine to hold overnight, even though my water was perfectly clear and I had no combined chlorine.
    16x33 fiberglass pool sand filter

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    I would say that I have to add an inch or so of water, not quite every day, but more often than every other day if that makes sense. I have not tested to see if the Chlorine holds over night though. I will try to do that this weekend, I have just been working too much. But if I don't have any CYA, my question has to be, would my Chlorine hold overnight? I did lose some CYA over the winter, that is a fact, but I have lost more somehow, and I did not think that this could be taken except through an algae infestation.

    At any rate, I added stabilizer, so it will take a couple of days really for that to equalize. When I lowered my TA, I literally connected my air compressor to the return jet and turned my pool into a hot tub. Could the direct introduction of air into the water chemically remove the stabilizer? I suppose that this is a molecular question.

    Introducing O2 into the water lowers TA, and also seems to raise PH, which I have to lower again with acid. If CYA is acid, does it get effected with this yoyo effect? I managed to lower my TA more than 100 doing this, so who knows?
    steve

    Above Ground / 18' Round / Vinyl Liner / Sand Filter / 100K Gas Heater / Salt Added / No Nature2

  5. Back To Top    #5
    My take on CYA is that it is 'sunscreen' for your chlorine, so if there is no sun, the Cl won't get burned (off) ... at least not as fast. You will probably get some loss, since it is still being used up to clean your water.

    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!

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    mbar's Avatar
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    I am not good with the chemistry - ChemGeek or Waterbear can answer these questions . The holding chlorine overnight is how you can tell if something is eating your chlorine other than sunlight. Cya stops the sun from burning off the chlorine, so if you have no cya, then testing the chlorine when the sun goes down, and first thing in the morning before the sun comes up is a way to tell if there is anything in the water consuming the chlorine, like algae or bacteria.
    16x33 fiberglass pool sand filter

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    Sounds like a plan. I will do that tonight and see how it goes.
    steve

    Above Ground / 18' Round / Vinyl Liner / Sand Filter / 100K Gas Heater / Salt Added / No Nature2

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