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Thread: A large drop in chlorine, but CC is 0

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    tedinelkgrove's Avatar
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    A large drop in chlorine, but CC is 0

    It seems like I am losing a lot of chlorine in short amount of time. I tested added chlorine Thursday evening ~5pm and level was ~10.5ppm. This morning I tested @ ~11am and the FC was 2.5. A loss of 8ppm in a full day of sun and 2 nights. My pool is not leaking; turned automated filler off for a few days before this and level stayed normal after 2 relatively warm-sunny days. I tested CC and color remainded clear after adding the R-003 reagent.

    Any thoughts. Could my volume be off? But then again, is 1-2k gallons going to break the bank here?
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    Re: A large drop in chlorine, but CC is 0

    What is your CYA level?
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    tedinelkgrove's Avatar
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    Re: A large drop in chlorine, but CC is 0

    Sorry:

    CYA=40
    TA=50 (needed low to combat pH drift)
    CH=280
    pH=7.8
    Borates=50
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    Re: A large drop in chlorine, but CC is 0

    At that CYA level, I would expect a loss a little less than that.

    How much swimmer load did you have during that period?

    Do the overnight FC loss test found in pool school to confirm you don't have organics in the pool.

    If you pass that test, you might bump your CYA up to around 50 to see if that slows your loss.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    tedinelkgrove's Avatar
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    Re: A large drop in chlorine, but CC is 0

    I lost 1.0 ppm over night. Took first reading at ~835pm when sun set; just took second reading at ~645am.
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    JasonLion's Avatar
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    Re: A large drop in chlorine, but CC is 0

    You might be fine or you might have some hidden algae. I suggest checking for hidden algae in obscure places that don't get good circulation. Some possible places to look include underneath or inside the ladder, inside light niches, in the auto fill chamber (if you have one), etc.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    tedinelkgrove's Avatar
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    Re: A large drop in chlorine, but CC is 0

    I rechecked CYA, being it has been a month+ since last time. It was below 30ppm, so I added ~1lb of stanilizer. We'll see in a few days if it helps.
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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