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Thread: Low PH with CYA of 60 how much FC can I have without risk of damage to the liner

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    Low PH with CYA of 60 how much FC can I have without risk of damage to the liner

    I have a pool with sub 7.0 PH. FC is 11pm. It has green algae and I want to shock it. The CYA is around 50ppm. How much chlorine can I safely add? Obviously I have added PH Up and will wait but wondered what the tolerance or risk is in this case to the liner.
    Glenn - Pickering, Ontario
    Circa 1980 Vinyl In-ground 80,000 Ltrs. ~ K2006 Kit ~ Hayward Pump/Navigator/Sand Filter ~ Raypak 255 Gas Heater

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    Richard320's Avatar
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    Re: Low PH with CYA of 60 how much FC can I have without risk of damage to the liner

    You may safely go to shock level with no damage to your liner.

    For 50 CYA, shock level is 20FC. Pool School - Chlorine / CYA Chart

    If you look at this graph stolen from Pool Water Chemistry


    You can see that 1 FC at zero CYA - less than tap water has - has the same unbuffered chlorine content as about 40 FC with 50 CYA.
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