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Thread: HELP: lost most of FC over night

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    HELP: lost most of FC over night

    I brought my FC up to 13.5 ppm last night.
    I added 2 full gallons from around 3pm(zero FC)->till 8:30 when I hit 13.5 ppm.
    This morning at 7:30am FC was down to 2 ppm, water still looks perfect.
    do I just go back to 12-13 ppm? was that enough since it ate most of the FC over night?

    CYA = 30 ppm
    FC NOW = 2 ppm
    CC = .5
    TA = 180
    PH = 7.2
    CYA = 25-30

    I assume other numbers are not a matter at this point. I did all tests late yesterday and they are posted above.
    I did RE check the CYA, in case i had it too LOW. first check was 25, 2nd test was 25-30ppm(8pm last night)
    27" round AG (vinyl)
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    1.5 hp pump
    new zeobrite sand this year(100 lbs)
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    BoDarville's Avatar
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    Re: HELP: lost most of FC over night

    drdispatch:

    If you lost 11.5 ppm FC overnight, something is definitely living in your pool even though whatever it is hasn't made itself visible. That amount of FC loss is not unusual when beginning the Shock Process. I would dose FC back up to between 12-13 ppm. That level is enough to do the job without being overly harsh on your pool's finish & equipment. The secret is that you have to keep FC at that level at all times in order to do the job effectively. This means testing FC multiple times a day. See The Shock Process link in my sig for more details. The FC loss will eventually drop as more of this organic matter is killed off.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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    Re: HELP: lost most of FC over night

    Yes, go back to about 13FC and maintain shock level. Something is eating your chlorine.

    Check all the hiding places, ladders, skimmer, light niche, etc

    Are you brushing the pool?
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    Re: HELP: lost most of FC over night

    I work from home so testing during day is no prob.
    did NOT brush the pool this time. will do that this round.
    don't see any signs of anything in skimmer or around light.

    this is one of those ladders that partially fills legs with pool water...could that be the 'lair'?
    pull it out for now?

    test every 2 hours or 1 hour?
    27" round AG (vinyl)
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    WaterWay 22" sand filter
    1.5 hp pump
    new zeobrite sand this year(100 lbs)
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    Re: HELP: lost most of FC over night

    It seems that while you reached a level of 13ppm FC at 8:30, you implied you'd been adding small amounts of chlorine (equivalent to 1.5 quarts per hour throughout the afternoon and evening).

    We must assume that some portion of that FC was continually and gradually consumed by killing a small amount of the algae slowly during those 5 .5 hours.

    Considering your overnight FC loss, you will have to continue the shock process as stated above, doing your best to maintain the 13ppm level as consistently as possible.

    As you lost 11.5ppm overnight, you may assume that in sunlight you will lose FC even faster.

    Testing every hour or two (to get an idea of the speed at which you lose FC as it kills the algae) may help you understand the shock process, its requirement for consistency and timing, and keep you ahead of the algae.

    Keep up the good job.
    Alan in Wellington, FL - near West Palm Beach
    15,200 gal IG, painted plaster, 1988; 200 SqFt cartridge filter, 2013; 1.5 HP 1-speed pump (uprated), 2005; heat pump, 2005;
    soon to repair (dead) SWG AquaRite T-15 cell, 2005, and replace (dead) suction-side cleaner, 2005.
    Almost everything died this winter 2012-'13, and I know we shouldn't complain... but, Arrgh!

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    Re: HELP: lost most of FC over night

    thanks guys

    I did add chlorine in steps. was not intended to go down that way. did not think I was gonna need to shock it

    I had zero from refill and wanted to start with 4 ppm->3 pm->dose 1
    by 5 pm was 1.5 so added more per calc to hit 10 ppm->dose 2 (shock time per posting here)
    6:45 was 9.5 ppm
    8 pm was 9 ppm-> added 80 oz (using 12.5%)-> dose 3
    8:30 FC = 13.5, sun was down by then so recorded that for test this morning

    Used 3 full gallons of 12.5% from 3 pm to 8 pm

    gotta go buy more, only have 1 left
    will hit when I get back

    again thanks for quick replies, will post as I go here
    27" round AG (vinyl)
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    WaterWay 22" sand filter
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    new zeobrite sand this year(100 lbs)
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    Richard320's Avatar
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    Re: HELP: lost most of FC over night

    Quote Originally Posted by drdispatch
    I work from home so testing during day is no prob.
    did NOT brush the pool this time. will do that this round.
    don't see any signs of anything in skimmer or around light.

    this is one of those ladders that partially fills legs with pool water...could that be the 'lair'?
    pull it out for now?

    test every 2 hours or 1 hour?
    It's a classic spot. Inside the legs or beneath the rungs. Pull the ladder and clean it out somehow. Then set it in there to soak while you're at shock level.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: HELP: lost most of FC over night

    Quote Originally Posted by drdispatch
    this is one of those ladders that partially fills legs with pool water...could that be the 'lair'?
    Yes, very likely. Nooks and crannies within ladders provide a hiding place for algae due to low water circulation relative to the rest of the pool.
    Quote Originally Posted by drdispatch
    pull it out for now?
    I would. Suggest giving it a good cleaning with a bleach/water solution while it's out.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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    Re: HELP: lost most of FC over night

    ......this is one of those ladders that partially fills legs with pool water...could that be the 'lair'?
    pull it out for now?
    Yep, could be the culprit

    Can you use a turkey baster or something to shoot some bleach in the holes? If not, you could take it out and inspect/clean it.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: HELP: lost most of FC over night

    I'm on it boys!!
    just got 8 more gallons of 12.5%. gonna bring it back up to 13-14ppm, then check hourly and adjust
    going to pull ladder from pool until I pass OCLT test, then clean and put back

    what do you guys do overnight? do you do last dose heavy to account for what it eats till morning?...or?
    27" round AG (vinyl)
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    new zeobrite sand this year(100 lbs)
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    Re: HELP: lost most of FC over night

    Overnight last night, you lost approximately 1 ppm FC per hour consumed by the algae killing process. If you keep the FC level up to shock level today, you'll likely lose less than 1ppm per hour overnight tonight.

    Just check it as late as possible and get the FC number up to 13 at that time. Then check it as early as possible in the morning and do it again!

    For being prepared with sufficient chlorine to shock, I usually assume that after a full 24 hours of shock level FC, each day I'll need to have on hand 2/3 the chlorine amount of the previous day. That's just for the shopping list, of course. You still must test the water, because you might go thru the chlorine faster or slower depending on the rest of your water chemistry.

    You are on the right track.

    (BTW, here in S. FL., in our 15K gal pool, I use just over a quart of 10% chlorine daily to maintain.)
    Alan in Wellington, FL - near West Palm Beach
    15,200 gal IG, painted plaster, 1988; 200 SqFt cartridge filter, 2013; 1.5 HP 1-speed pump (uprated), 2005; heat pump, 2005;
    soon to repair (dead) SWG AquaRite T-15 cell, 2005, and replace (dead) suction-side cleaner, 2005.
    Almost everything died this winter 2012-'13, and I know we shouldn't complain... but, Arrgh!

  12. Back To Top    #12

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    Re: HELP: lost most of FC over night

    FC is now at 18.5 ppm
    was to the ounce per the calc, I think this is fresh batch of 12.5% is why.
    still should be guaranteed kill at that level.
    ladder is out
    pool has been scrubbed
    will let it drop to 14ppm. not much sun today, may last most of the day, will see
    27" round AG (vinyl)
    17,000 gal
    WaterWay 22" sand filter
    1.5 hp pump
    new zeobrite sand this year(100 lbs)
    pool rover

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    Re: HELP: lost most of FC over night

    ok, thought I would post the shock data for day 2 & 3, this may help guide someone else on the process and appetite this stuff has
    I aimed for shock level of 14ppm through the process.
    on 6/3 I added my first liquid chlorine, first to reach min FC level, then raised to shock level late in day on 6/3.

    PH = 7.2
    CC has been from 2ppm _>zero, today its zero
    only listing FC below as other numbers are fine for now.

    NOTE: 2 major mistakes I made on day 1:
    A)did not remove ladder, I feel it had water trapped in legs that was feeding stuff back into the pool.
    B) did not brush pool, old brush was shedding bad, got new brush and brushed 2 times yesterday, once today.

    6/4->7:30am->went from 13.5 ppm FC down to 1.5 ppm over night
    6/4->11am-> added 228oz of 12.5%(gap in time due to getting more liquid)
    6/4->11:30am->FC = 18.5 ppm
    6/4->Noon->FC= 14 ppm
    6/4->1pm->FC = 9.5 ppm-> added 80oz 12.5%
    6/4->1:20pm->FC = 17 ppm(tested so soon to verify)
    6/4->3pm->FC = 14
    6/4->5pm->FC=12.5 ppm
    6/4->7pm->FC=10.5ppm->added 60oz 12.5%
    6/4->8:30pm-> added 32 oz MORE to raise FC for overnight
    6/4->9pm->FC=15ppm (last test till morning)
    -------------------------------------------------
    6/5->7:30am->FC = 11ppm(only lost 4ppm overnight)
    6/5->8am->added 52oz 12.5% to hit 14ppm again

    from here will check at noon and 4pm, add bleach as needed, 8pm will make sure at 14ppm and hope for no loss overnight.
    water is still crystal clear, has been entire time. had I not looked for FC loss overnight 2 nights ago, would have thought all was good....was NOT.

    I have used 6 gallon plus 6 cups of 12.5% since I started Monday(6/3), about $30, not bad!!
    will post what happens as I go through what I hope is last day of shock process.

    this would have been an all summer long nightmare using pool store. if you cant check your FC accurately every hour or so you will probably lose the battle(get that TF100), for me thats near 20 mile round trip to pool store each time, not to mention all the goodies they would have me buy, plus the frustration.
    BBB is well worth the small effort it takes
    27" round AG (vinyl)
    17,000 gal
    WaterWay 22" sand filter
    1.5 hp pump
    new zeobrite sand this year(100 lbs)
    pool rover

  14. Back To Top    #14
    Butterfly's Avatar
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    Re: HELP: lost most of FC over night

    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  15. Back To Top    #15

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    cant seem to get proper FC

    Merged threads. Best to keep all info in this thread until completely done. Folks need to see the history ...Thanks, Butterfly

    I have been posting and shocking since Monday. This is my first round with BBB, had my pool 7 years.
    I have everything written down, shock target level = 12 ppm
    CYA = 30
    PH =7.5
    TA = 180
    CH = 220
    FC = 11.5 as of 6:30 am

    i have maintained 12-14ppm all week, pump running 24 a day
    been brushing pool
    ladder has been out entire time
    water has looked perfect since day 1

    yesterday was best day, only lost 2 ppm wed night(15.5ppm)->thur morning(13.5ppm), by noon thursday FC= 12.5 ppm
    by 4pm thursday FC was 12ppm, I had added NO bleach yet that day due to sustained levels being ok.
    only lost 1.5ppm for entire day!
    was cloudy, 68 deg, had a few sprinkles yesterday as well.

    by 7pm thursday evening FC = 8.5 (biggest drop of day..hmmm)
    added 96oz, retested FC at 8:30pm, was 15 ppm
    this morning FC was down 11.5, lost 3.5ppm overnight?

    why would this lose so little during day, was hoping to pass OCLT last night, instead I lost ground?
    could the .004 of rain do that?

    I just upped FC to about 16ppm to try and kill this, will maintain that all day

    advice? anyone?
    27" round AG (vinyl)
    17,000 gal
    WaterWay 22" sand filter
    1.5 hp pump
    new zeobrite sand this year(100 lbs)
    pool rover

  16. Back To Top    #16
    Richard320's Avatar
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    Re: cant seem to get proper FC

    Maybe there's a lot of organic debris in the pump strainer or the filter. Chlorine is an oxidizer - it burns stuff chemically instead of with a flame. When's the last time you backwashed and cleaned the basket? No chance a bunch of crud washed off a roof and into the pool? That's all I can think of.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

  17. Back To Top    #17

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    Re: HELP: lost most of FC over night

    will ck the strainer, there were a few leafs a day or so ago.
    I have no real trees in the pool area, no roof, nothing overhead period.
    backwashed filter a few times this week, not much to clean, sand is few weeks old.

    strange though, would not think anything would take root at even the min FC I had was 8.5ppm.

    any who added enough to account for 4ppm loss to sun, plus a few ppm to raise shock level
    27" round AG (vinyl)
    17,000 gal
    WaterWay 22" sand filter
    1.5 hp pump
    new zeobrite sand this year(100 lbs)
    pool rover

  18. Back To Top    #18

    Re: HELP: lost most of FC over night

    Any chance your CYA number is wrong? If your CYA is much higher than you think, your shock level may not be sufficient.
    20K IG White Plaster - Hayward 1.5 HP Pump - Anthony DE Filter - TF100 Test Kit

  19. Back To Top    #19

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    Re: HELP: lost most of FC over night

    good point.
    I got my kit monday, tested it twice to make sure. was 111 by pool store test, hit 150ish last summer
    drained pool down to 17" deep, then refilled last friday.
    test was between 25-30 both times, when I lost sight of black dot.

    will test it again now. I always have this kind of luck.."really ..that never happens!"

    I got speedstir at 4pm yesterday(mail), unless its changing my results..maybe I was not swirling water good enough by hand.
    who knows. will post what goes on. I have not tested FC since I added this morning. will do that so I have a baseline to compare to come evening test/dose
    27" round AG (vinyl)
    17,000 gal
    WaterWay 22" sand filter
    1.5 hp pump
    new zeobrite sand this year(100 lbs)
    pool rover

  20. Back To Top    #20

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    Re: HELP: lost most of FC over night

    re tested...
    CYA is closer to 20 then 25. I can still see dot at 25, but barely, pretty well gone at 20

    FC is now 13, was 11.5 at 6:30am, added 80oz of 12%, seems like it should be higher then that. sun is out more then not today, buy only 70deg.
    I realize I will need some CYA later to keep sun off it.
    need to get this killed first.
    think I need to add more FC to get well above shock level for the day or leave alone and monitor?
    27" round AG (vinyl)
    17,000 gal
    WaterWay 22" sand filter
    1.5 hp pump
    new zeobrite sand this year(100 lbs)
    pool rover

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