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Thread: CYA and FC levels

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    CYA and FC levels

    Hi Everyone!

    When I started doing this pool thing on my own last month, my pool actually had 0 CYA in it (the pool guy we had for one year never added any). On Sunday, March 31, I added a gallon of liquid CYA to the pool. 2 days later, my CYA level was at 50. 3 days after that, it was at 40 and today I just measured it around 30. It seems like my CYA levels are going down as the weeks go by. Along with that, my FC levels have gone up. I was just wondering if it is normal for CYA to fall like that, especially when the pool started with 0 to begin with? Should I add more or should I wait until I get my FC at the correct level? Below are all of my numbers, just for a reference.

    FC: 8
    CC: 0
    pH: 7.8
    TA: 125 (Working to bring this down by adding acid daily, but also keeping an eye on my pH and aerating when needed)
    CH: 1000+
    CYA: (+-10) 30

    After adding the CYA a couple of weeks ago, my FC was at 6.5 and CYA was around 50. I was trying to go for the target range of FC 4 and CYA 60 (based on the chlorine/cya chart). I reduced the percentage on my SWCG to hopefully make sure my FC doesn't keep climbing and plan on emptying some of the pool next week to reduce CH (I live in the Santa Clarita Valley, CA -- SoCal, so from what I've read here, I shouldn't be too worried about emptying less than half of the water....). But until I do empty the pool, I still want to work hard and keep these chemicals in check.

    Thanks for your help!
    13,000 gallon plaster salt water pool. Jandy DEV60 filter, Jandy AquaPure SWG (APURE1400)

  2. Back To Top    #2
    Mod Squad woodyp's Avatar
    Join Date
    Apr 2010
    East Texas

    Re: CYA and FC levels

    How is your water being tested and by who? Have you added or drained any amount of water since first testing?
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  3. Back To Top    #3

    Re: CYA and FC levels


    I am testing my water (before, my pool guy just used strips and was the one who said that, with a salt water pool, you don't need CYA... nice!). I have been using the Taylor K-2006 kit. I have not drained my water yet, but it does have an auto-filler so there is a possibility that some water has come in if the level dipped down at all.
    13,000 gallon plaster salt water pool. Jandy DEV60 filter, Jandy AquaPure SWG (APURE1400)

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: CYA and FC levels

    You could try turning off the auto-fill for a while and seeing if the water level is dropping faster than just evaporation. Either water being replaced or testing error are about the only way for the CYA to drop.
    Jason, TFP Moderator
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  5. Back To Top    #5

    Re: CYA and FC levels

    Ok perfect- I'll shut off the auto filler and test. Thank you!
    13,000 gallon plaster salt water pool. Jandy DEV60 filter, Jandy AquaPure SWG (APURE1400)

  6. Back To Top    #6

    Re: CYA and FC levels

    It is very unlikely that there is a leak and the CH is that high. THe CYA test in my opinion is very subjective, so it is probably just normal variance in testing cya

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