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Thread: FC/CC question

  1. Back To Top    #1

    Join Date
    Aug 2008
    Location
    Central CA, USA
    Posts
    25

    FC/CC question

    Hi all,

    I am a bit confused about my chlorine testing. Here are my overnight numbers:

    8:30 pm

    FC-20.5
    CC- .5
    TC-21.0

    5:45 am

    FC-13.5
    CC- .5
    TC-14.0

    It's obvious that I still have algae ( -7 FC overnight ). What I don't understand is why my CC's are so low. I have the pool sweep running constantly with the filter. Can it be cleaning it up that fast?


    Readings from 8/24 before the shock process started:
    FC- .5
    CC- .5 ( This is when I realized my SWG is not working properly!)
    TC- 1
    pH-7.5
    TA-130
    CH-410
    CYA-60

    Yep! My water has issues!

    poolcarma (Just keep scrubbing, just keep scrubbing.)
    Poolcarma

    Free form 13,000 gal. in-ground pebble-tec pool, Pentair Aquatech 60 square ft. DE filter, Pentair WhisperFlo 1.5 HP Pump, Chlorine Factory Model R40 salt water chlorine generator.
    Hayward Navigator pool sweep.

  2. Back To Top    #2

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,084

    Re: FC/CC question

    What I don't understand is why my CC's are so low.
    Combined Chloramines are a good indicator that you do have algae but they are not neccessarily an indicator that you don't have algae. A little confusing, huh? I'm good at that.

    A CC test result of 1.0 or greater is almost a dead giveaway your pool needs to be shocked. Others here can explain the chemistry more clearly than I.

    However, algae can (and does in your case) easily exist without the presence of CC's. Again, perhaps we'll get some help explaining the chemistry
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3
    JasonLion's Avatar
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    May 2007
    Location
    Silver Spring, MD
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    37,879

    Re: FC/CC question

    When fighting algae, CC is constantly being both created and broken down. When chlorine first contacts the algae it forms CC. Then additional chlorine breaks down the CC. CC only shows up on the test when it is being created more quickly than it is being broken down.

    As long as you are maintaining reasonably high FC levels, CC will typically be broken down more quickly than it is being created. CC tends to accumulate at relatively low FC levels, when there is enough chlorine to kill algae, but not enough to break down the resulting CC.
    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

  4. Back To Top    #4

    Join Date
    Aug 2008
    Location
    Central CA, USA
    Posts
    25

    Re: FC/CC question

    Thanks!

    I'm glad something about my water makes some sense!


    Since we're talking chlorine.........

    It's still very hot (over 100 degrees)and sunny where I am, and I'm wondering about chlorine loss during the day. Since I'm trying to maintain shock levels, should I go out every hour or so and check the chlorine? Should I shock at a higher level?

    Thanks for your help!
    poolcarma
    Poolcarma

    Free form 13,000 gal. in-ground pebble-tec pool, Pentair Aquatech 60 square ft. DE filter, Pentair WhisperFlo 1.5 HP Pump, Chlorine Factory Model R40 salt water chlorine generator.
    Hayward Navigator pool sweep.

  5. Back To Top    #5
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879

    Re: FC/CC question

    I suggest testing and adding chlorine every hour until the FC level starts to mostly hold. Once FC is remaining at 80% or higher of it's original value after an hour you can switch to three times a day.
    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

  6. Back To Top    #6

    Join Date
    Aug 2008
    Location
    Central CA, USA
    Posts
    25

    Re: FC/CC question

    Thanks, I'll keep keepin' on!

    poolcarma
    Poolcarma

    Free form 13,000 gal. in-ground pebble-tec pool, Pentair Aquatech 60 square ft. DE filter, Pentair WhisperFlo 1.5 HP Pump, Chlorine Factory Model R40 salt water chlorine generator.
    Hayward Navigator pool sweep.

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