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Thread: CYA of 0 on startup

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    CYA of 0 on startup

    Hey guys,

    I am new to pools and need some help. I have just started working on my water chemistry getting ready for summer. I took a sample to the pool shop and had it tested. I know I need a good test kit just haven't invested yet. The pool shop told me that my CYA level was 0 which was virtually impossible because it was 70 at closing and there was no way for it to go anywhere. The shop told me that I must have a very high chlorine demand and wanted to do an overnight test to evaluate. After calling back this morning she told me that I would need 33lbs of shock to overcome the demand from what the test showed. My water is pretty much balanced on the ph scale and after reading on here I would love to start using bleach for my shocking process but I want to know if this information is accurate? Can anyone point me in the right direction before I do something crazy and really get everything messed up? Thanks in advance.

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    Mod Squad jblizzle's Avatar
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    Re: CYA of 0 on startup

    Welcome to TFP!!!

    They are full of nonsense. They can not tell how much you need overnight.

    You really can not know what is going on until you have one of the recommended test kits. The CYA "might" be zero if it was converted over the winter, which would require a lot of bleach to get rid of. But pool stores are notoriously bad at the CYA test.

    What were the rest of the test results?

    You should not start adding a bunch of bleach until you can test the FC and CC. If the CC are high and the CYA is low, that would point to the conversion of the CYA to ammonia.
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    Re: CYA of 0 on startup

    According to the print out.
    Ph-7.2
    TA-80
    FC-0
    CC-0

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    Re: CYA of 0 on startup

    I would only trust your own CYA readings using a recommended test kit from here. It's the one pool stores continually get WAY wrong. Same with having CYA of 70 last year, you can't trust it unless you did tested yourself.

    CYA "can" be broken down over winter by bacteria but the process isn't totally understood and isn't common. Your first step is get a test kit and post results, that will prevent you from doing something crazy and getting everything messed up. If you're in a pinch you can get a 5-way test kit from walmart that can test CYA 2 times, with that you can at least know your CYA. But without a FAS-DPD chlorine test you won't be able to truly know what your FC is when shocking.
    18x36 inground vinyl lined, Hayward sand filter and tablet chrolinator, approx 18k gallon

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    Mod Squad jblizzle's Avatar
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    Re: CYA of 0 on startup

    Well you certainly need bleach and you might need CYA. That is all you know right now.

    What does the water look like?
    Jason, TFP Moderator
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    Re: CYA of 0 on startup

    The water is cloudy but not green or anything. It is very hard to see bottom but if you look really close you can barely see it.

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    Mod Squad jblizzle's Avatar
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    Re: CYA of 0 on startup

    You certainly need to go through the shock process, even if the algae is not visible, there is something in the pool:
    Defeating Algae
    Turning Your Green Swamp Back into a Sparkling Oasis
    Shocking Your Pool
    Jason, TFP Moderator
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    Re: CYA of 0 on startup

    I have read on another post that it would be a good option to raise the FC up to 10ppm and continue to raise it to that until I can maintain a measurable chlorine level? Is this correct?

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    Mod Squad jblizzle's Avatar
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    Re: CYA of 0 on startup

    That is a start, assuming that your CYA is actually less than 20ppm.

    If it is truly zero, I would not suggest keeping it even as high a 10ppm for very long.
    Jason, TFP Moderator
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