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Thread: FC level not dropping when trying to shock

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    FC level not dropping when trying to shock

    Pool very green. I have studied Pool School and I think I understand all the concepts. I ordered and received the TF test kit.
    My CYA was nearly zero so I added enough to get it to 40. I left town for a few days while the CYA dissolved. This morning I tested
    and CYA was 40-45 which calls for about 16ppm shock level. I added 4 jugs of bleach (8.25% at 121oz per jug) according to the Pool Calculator. I waited half an hour and tested FC but still 16.5. I waited another half hour and still 16.5. Why isn't it dropping?
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Mod Squad Bama Rambler's Avatar
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    Re: FC level not dropping when trying to shock

    Is your pool clear green or cloudy green?

    Did you run an OCLT to determine if you had something growing?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: FC level not dropping when trying to shock

    OK. I thought I had read everything in triplicate but missed the OCLT part. Pool is cloudy green...can just make out the top of the light.
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Mod Squad Bama Rambler's Avatar
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    Re: FC level not dropping when trying to shock

    That's ok, since it's cloudy green that indicates the need to shock. Wait till last thing to run the OCLT.

    Check the FC again in about an hour and see if it's dropped. It may not be consuming the FC very fast.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: FC level not dropping when trying to shock

    OK...I did study about the overnite test earlier and understand. Just started the process this morning. Added bleach at 9:30am. Tested at 10am and FC was 16.5. Tested again at 1030am...still 16.5. Now just tested at 11:15am and it's now 15.5.
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Mod Squad Bama Rambler's Avatar
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    Re: FC level not dropping when trying to shock

    Just keep checking it every hour or two and bring it back to about 16.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: FC level not dropping when trying to shock

    While I'm waiting to test FC again, I have another question. Is there a recommended method of adding bleach to the pool? I started by pouring a jug around the edge, then another jug at arm's length then poured the other two jugs into a bucket and spread across the middle of the pool. How long does it take for the bleach to become evenly distributed throughout the pool?
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Mod Squad Bama Rambler's Avatar
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    Re: FC level not dropping when trying to shock

    You should pour it slowly in front of a running return. If you do that it takes about 30 minutes to become completely integrated in the pool water. It's probably faster than that, but 30 minutes makes sure it's enough time.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: FC level not dropping when trying to shock

    Running return would be the skimmer or the bottom drains?
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Mod Squad Bama Rambler's Avatar
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    Re: FC level not dropping when trying to shock

    Returns are jets where the water is flowing out into the pool (i.e. returning to the pool from the pump).
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: FC level not dropping when trying to shock

    OK. That makes sense. Thanks!
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Re: FC level not dropping when trying to shock

    Two tests in a row and the FC dropped to 13. May be from sunlight but have had mostly clouds so far. I guess the UV probably penetrates the clouds anyway. Anyway I'm now in the process of maintaining shock level.
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Re: FC level not dropping when trying to shock

    Is it abnormal for my FC level to be dropping only to the 13-15 range after testing and adding bleach every hour for the last 9 hours? No FC change on a couple of them. My shock level is 16 and I've been padding it to 18. Not seeing any improvement yet. Too early?
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Mod Squad jblizzle's Avatar
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    Re: FC level not dropping when trying to shock

    You need POP: Pool Owner Patience.

    Just be happy you are not having to use gallons of bleach every hour.
    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
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Re: FC level not dropping when trying to shock

    POP absolutely but you are on top of it. The more you keep it at 16 or slightly over the faster you will see improvement. Keep it up.
    In ground 25,000 gallon - vinyl liner - Sand filter - residential pool
    Also maintain two commercial 190,000 gallon competitive indoor bromine facilities -9x Sand filters

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    Re: FC level not dropping when trying to shock

    Thanks to all! I've got POP but, being new to this, I just didn't know what to expect.
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Re: FC level not dropping when trying to shock

    Is the CYA test valid under high FC levels? Maybe I should re-check it? Just read about re-mixing a few times and checking the levels. Also I did it indoors rather than outdoors.
    Date of Build: Dec, 2009 near Atlanta; 17000 gal; IG vinyl; SWG w/ sand filter; Hayward Super Pump 3/4HP

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    Mod Squad jblizzle's Avatar
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    Re: FC level not dropping when trying to shock

    The CYA test is not affected by the FC.

    You can pour the mixture back and forth a few times to see if you get the same answer ... and outside with your back to the sun is the proper lighting.
    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
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: FC level not dropping when trying to shock

    Quote Originally Posted by dlwxman
    Is the CYA test valid under high FC levels? Maybe I should re-check it? Just read about re-mixing a few times and checking the levels. Also I did it indoors rather than outdoors.

    The recommended way to test CYA is outdoors, with sun shining, back to the sun, test tube at waist level.
    8,000 gallon, in ground, fiberglass pool with a cartridge filter.

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    Re: FC level not dropping when trying to shock

    Quote Originally Posted by dlwxman
    Is the CYA test valid under high FC levels? Maybe I should re-check it? Just read about re-mixing a few times and checking the levels. Also I did it indoors rather than outdoors.
    CYA testing is not affected by Chlorine levels. Proper lighting is essential. Outdoors when the sun is high is best. Turn your back to the sun so the vial is shaded and hold at waist level looking straight down at the dot as you pour. Clouds, sun down low will give you different results as will testing indoors.
    Bill
    18'X4' 7600 Gal AG
    3/4 HP Pentair Pump
    Hayward S166T 100 lb sand filter

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