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  • Chlorine / CYA Chart

    Perhaps a cornerstone element of TFPC is understanding the relationship between the chlorine in your pool and the stabilizer you put in to protect the chlorine from the sun. Generally, the more stabilizer, the more chlorine you need to maintain its effectiveness. The charts below show the recommended relationship for outdoor residential pools.

    Non -SWG Pools

    CYA (Stabilizer) Minimum FC Target FC Shock FC
    20
    2
    3
    10
    30
    2
    4
    12
    40
    3
    5
    16
    50
    4
    6
    20
    60
    5
    7
    24
    70
    5
    8
    28
    80
    6
    9
    31
    90
    7
    10
    35
    100
    7
    12
    39

    SWG Pools

    CYA (Stabilizer) Minimum FC Target FC Shock FC
    60
    3
    4
    24
    70
    3
    5
    28
    80
    4
    6
    31

    The shock levels shown have equivalent effective disinfecting chlorine amounts. At high CYA levels it may be impractical to use such high FC levels, lower FC levels are often sufficient though they take longer to kill algae. At very high CYA levels, over 80, a partial drain/refill to lower the CYA level is usually required.

    Most saltwater chlorine generator (SWG) pools appear to prevent algae at a lower minimum FC level compared with the minimum FC column for manually dosed pools.

    For indoor pools we recommend CYA between 20 and 30. The reasoning for using CYA indoors is quite different. For more information please ask on the forum.

    Acknowledgment: The original Chlorine/CYA "Best Guess" chart was developed by Ben Powell. Richard Falk (chem geek) has refined and expanded on that original to produce the Chlorine/CYA Chart by Chem Geek based on experiences with members on this forum and the old Pool Forum and conformation to chemical theory.

    TroubleFreePool.com 2014