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Thread: FC Test Weirdness

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    Join Date
    Jun 2015
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    Question FC Test Weirdness

    Hello,
    I'm having something rather strange happen with my TF-100 test kit.
    I'm doing a bucket test (2gal pool water, 1/4 tsp bleach), and using the FAS/DPD drop test for FC.

    I add the powder, then swirl, then add 4 drops of the R-0871 liquid. It neutralizes the pink color.
    But then if I wait a minute, the pink color slowly comes back. I can neutralize it again with a couple of drops of the R-0871, but it will come back again.

    If I can't even trust my basic FC test, I'm worried. Thank you for helping me figure out what's going on.

    (background - I just returned from vacation to no chlorine, and all the CYA gone too; likely converted to ammonia. Algae starting to grow)

    Hawk
    40,000 gallon, in-ground plaster pool. DE filter. Opaque electric cover, normally closed. Boise Idaho.

  2. Back To Top    #2
    Richard320's Avatar
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    Re: FC Test Weirdness

    "If left sitting on the counter, the sample will turn pink again one or two minutes after the test is completed. This is normal."

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  3. Back To Top    #3

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    Re: FC Test Weirdness

    As Richard noted, this is normal. It's due either from high CC bleeding through or just from oxygen in the air getting into the water and oxidizing the DPD dye. If you didn't measure high CC, then it's most likely the latter (i.e. oxygen in the air).
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Mod Squad jblizzle's Avatar
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    Re: FC Test Weirdness

    What is this bucket test I keep seeing mentioned about adding chlorine to a bucket of water? What is the point of the test?
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  5. Back To Top    #5

    Re: FC Test Weirdness

    It's a measured amount of pool water that you keep adding chlorine to until whatever is in the water is fully oxidized. It gives you an idea of how much chlorine you will need to add to the pool to resolve whatever issue you're trying to fix.

  6. Back To Top    #6
    Mod Squad jblizzle's Avatar
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    Re: FC Test Weirdness

    Does this then make people think they should add it all at once to the pool? Seems easier to just follow the SLAM process
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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  7. Back To Top    #7

    Re: FC Test Weirdness

    In most cases it's probably not worthwhile. It might be useful in a very limited number of cases.

  8. Back To Top    #8
    JoyfulNoise's Avatar
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    Re: FC Test Weirdness

    I've only heard of it (the bucket test) used when ammonia is suspected as being present. It gives you an idea of how much chlorine it will take to neutralize the ammonia and hold FC.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: FC Test Weirdness

    If you know about how much chlorine it will take to clear your pool, it can help determine the cost effectiveness of a drain and also a rough gauge of how long a SLAM may take. It is easily done, but not a test to be recommended right off the bat to all. Bucket tests can be very useful, especially for metals.

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    duraleigh's Avatar
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    Re: FC Test Weirdness

    The point of the thread is that OP needs to SLAM the pool. We are getting him FAR off track.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  11. Back To Top    #11

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    Re: FC Test Weirdness

    Duraleigh is right. Oops!

    Hawk: are you familiar with the SLAM procedure? If you need help, post a complete set of test results and we will advise.
    Happy slamming!

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