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Thread: High FC loss overnight!

  1. Back To Top    #1

    Join Date
    Aug 2011
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    Raleigh area, NC
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    High FC loss overnight!

    Morning!

    Thought I was doing great & decided to do OCLT last night. FC level went from 7ppm last night to 3 ppm this morning and CC=1ppm (it's been o or .5 all week) ugh...
    So I just shocked the pool according to the FC/CYA chart to get FC levels up to 12.

    FC: 3
    CC: 1
    pH: 7.5
    TA: 100
    CYA: 30ish

    Pool water looks & feels great, no slimy walls so I don't understand what happened. We've had company the past few days, so there have been extra people in the pool. My lowest FC read was 2.5 one afternoon, other than that it's been between 3-4 during the day and we bump to 7 at night.

    We are new pool owners (I posted last week in Just Getting Started to make sure we were starting off on the right path) and have used BBB method from day 1.

    Is this something I should expect after rigorous use? Is there a way for me to be more proactive? I just cringed this morning as I poured all that bleach (250 oz) into the pool.

    As always...you guys rock! Thanks for all your help.
    Robin
    14K; Hayward Pro-Series sand filter; 24' AG; 1.5 hp/ 2spd Power Flo Matrix Pump

  2. Back To Top    #2

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    Re: High FC loss overnight!

    Shock the pool. The CCs are too high.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

  3. Back To Top    #3
    Richard320's Avatar
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    Re: High FC loss overnight!

    Are you sure nobody snuck out for a midnight skinny dip?
    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: High FC loss overnight!

    Tested about an hour after shocking:

    FC: 12.5
    pH: high (possibly 8)
    TA: 90
    CYA: 30-40 (seems higher today than yesterday, we added CYA Sunday night...)

    I did not do CC test. According to Pool School I should shock at least twice, so I plan on doing that again tonight. I'll perform all tests again prior to shocking.

    Should I be concerned about high pH reading? I was reading around the site and consensus seems to be no- pH tests are inaccurate during shock levels.

    Any reason the kids shouldn't use pool this afternoon- I shocked around 9am?
    Robin
    14K; Hayward Pro-Series sand filter; 24' AG; 1.5 hp/ 2spd Power Flo Matrix Pump

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    WestSidePool's Avatar
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    Re: High FC loss overnight!

    To be proactive, add enough chlorine before your swim party to keep it above minimum, and test during if you have to.

    Keep in mind, shocking is a process. You have to keep your chlorine level up at shock level until you pass the three tests, otherwise your just wasting chlorine.

    -CC is 0.5 or lower
    -An overnight FC loss test shows a loss of 1.0 ppm or less
    -And the water is clear.

    It's safe to swim while shocking as long as the shock levels are at the recommended level with your CYA.
    Eric

    IG 17x33 Grecian - Vinyl Liner (21k gallons), Hayward Pro-Grid DE 4820 filter, Hayward Super Pump, CompuPool SWG CPSC36, TF-100 Test Kit

  6. Back To Top    #6
    Richard320's Avatar
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    Re: High FC loss overnight!

    pH can read wrong with high FC levels. Ignore it for now.
    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!

  7. Back To Top    #7

    Join Date
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    Raleigh area, NC
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    Re: High FC loss overnight!

    Thanks for the feedback. 1 pm test results show :

    FC 11.5
    CC .5
    pH 7.5- 7.8

    I feel better now. I did vacuum and backwash. I'm thinking that may also impact results but am not sure.
    Robin
    14K; Hayward Pro-Series sand filter; 24' AG; 1.5 hp/ 2spd Power Flo Matrix Pump

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    linen's Avatar
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    Re: High FC loss overnight!

    Quote Originally Posted by rme
    CYA: 30-40 (seems higher today than yesterday, we added CYA Sunday night...)
    CYA can take up to a week to show up in the test. I would use how much you think you put in to calculate your shock level for now. Test CYA again this coming Sunday/Monday and then adjust your FC levels to that.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    frogabog's Avatar
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    Re: High FC loss overnight!

    Now is the time to add .5ppm chlorine to raise it back to shock level.

    Falling below minimum even ONCE can cause this (happened to me about two weeks ago). The prevention is to never let it get that low, if you have to add a little more for high bathing load do it. It sounds like you caught it early enough to make it a one day shock process. But don't let it fall below shock (12ppm). Maintain shock level through today, do an OCLT with CC tomorrow morning and it will likely be all done. If not, one more day of maintaining won't hurt.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

  10. Back To Top    #10

    Re: High FC loss overnight!

    I'll bet the pool was digesting sunscreen and that is what consumed the chlorine.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

  11. Back To Top    #11

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    Re: High FC loss overnight!

    Quote Originally Posted by frogabog
    Now is the time to add .5ppm chlorine to raise it back to shock level.

    Falling below minimum even ONCE can cause this (happened to me about two weeks ago). The prevention is to never let it get that low, if you have to add a little more for high bathing load do it. It sounds like you caught it early enough to make it a one day shock process. But don't let it fall below shock (12ppm). Maintain shock level through today, do an OCLT with CC tomorrow morning and it will likely be all done. If not, one more day of maintaining won't hurt.

    I did not realize that when shocking I had to maintain the shock level throughout the whole day or time frame. I'll definitely keep that in mind from now on. For now I think the problem's been resolved.

    Thanks for everyone's help during my crisis!
    Robin
    14K; Hayward Pro-Series sand filter; 24' AG; 1.5 hp/ 2spd Power Flo Matrix Pump

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