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Thread: FC is disappearing overnight!

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    FC is disappearing overnight!

    We switched from Baquacil to the BBB method this spring. We got our CC down to 0-0.5, were keeping our FC levels steady.

    So since our FC was staying overnight and our CC were 0-0.5 we changed out our sand from what we had used last season with the Baquacil.

    But since doing that on Saturday, our FC keeps evaporating overnight!

    Here is what I got when testing this morning:

    FC-1PPM
    CC 0.5
    TC=1.5
    TA=150 (down from 250)
    PH 6.8
    CYA 50

    We are using the TF-100 test kit. Am I just not adding enough chlorine since changing out the sand to keep it at the 15ppp? I'm using the pool calculator but perhaps we are not adding enough at one time.

    We are using the 8.25%-121 oz chlorine when we add it. And when in the past I've added that at 3 containers a time, I'm getting up to the 15ppm. But then since the change in the sand, it's going away overnight.

    I'm getting a bit frustrated and am wondering where I've gone wrong-perhaps just not enough chlorine at a time?
    12K AG, Vinyl Oval Pool, Swim Pro Sand Filter, Pentair Opti-Flo High Performance Pump-HP 2.0 SPL, New Vinyl liner June 2015

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    Mod Squad Bama Rambler's Avatar
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    Re: FC is disappearing overnight!

    Are you testing about 30 mins after the addition to make sure you got to the target level?
    Dave J. TFP Moderator
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    Re: FC is disappearing overnight!

    It may be difficult to reconstruct why it happened but the important thing is to get the chlorine back to 15 ppm before you get an algae bloom.

    I assume your water is crystal clear?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: FC is disappearing overnight!

    Our water is crystal clear and I am testing again after putting in the chlorine and the levels go right up and with the quick test are in the 5-10 range.
    12K AG, Vinyl Oval Pool, Swim Pro Sand Filter, Pentair Opti-Flo High Performance Pump-HP 2.0 SPL, New Vinyl liner June 2015

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    Re: FC is disappearing overnight!

    I also just want affirmation from someone out there that it's normal to be putting this much chlorine in on a daily basis. Once we do get our FC level up to what we need. Is it normal to continue to need to add chlorine daily? We do have full sun during the day which is why I was working to get our CYA up from zero to the 50 range.
    12K AG, Vinyl Oval Pool, Swim Pro Sand Filter, Pentair Opti-Flo High Performance Pump-HP 2.0 SPL, New Vinyl liner June 2015

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    Mod Squad jblizzle's Avatar
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    Re: FC is disappearing overnight!

    Yes you need to add chlorine every 1-2 days so it does not drop too low.

    It is normal to lose 2-3ppm of FC everyday .... so that would mean needing to add about 54oz of 8.25% bleach each day.
    Jason, TFP Moderator
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    Re: FC is disappearing overnight!

    No one mentioned the pH. 6.8 is too low, you should aim for at least 7.2. Also, most pH tests only go down to 6.8, so it really could be lower. Are you actively lowering the TA, and using aeration to raise the pH? If not, you should get that pH up.
    John
    7 year old ~13,500 gal 24' AGP with 1.5 hp Proline pump, 150 sqft Pleatco cartridge, filled with well water with pH of about 4.5.
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    Re: FC is disappearing overnight!

    We are working on the TA as well. We've added muriatic acid twice and then aerated the heck out of the pool. The TA has come down quite a bit from a high of 280 to it's current level. Should I be working on getting it lower while I'm still trying to keep some FC in the pool and adding the chlorine? My PH reading tonight has gone back up to 7.2 as but I'm still at 1 PPM on the FC after adding 3 gallons of the 8.25% (121 oz bottles) today. My husband ran out to get more so that we can add more overnight.
    12K AG, Vinyl Oval Pool, Swim Pro Sand Filter, Pentair Opti-Flo High Performance Pump-HP 2.0 SPL, New Vinyl liner June 2015

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    Re: FC is disappearing overnight!

    If your not shocking your pool you should never let your fc drop below 4 ppm with a cya of 50 ppm......Mike
    18x52 intex ultra frame pool 6981 gallons, 1 HP LL pump with 19 in sand filter,BBB method,borax 50ppm
    leslies DPD test kit + fas-dpd chlorine test kit + borates test strips
    thru wall skimmer,hard plumbed with 2 returns 1 1/2 sch 40 pvc
    1 large fountain 1 inch sch 40 pvc,shut off ball valves on all

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    Mod Squad zea3's Avatar
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    Re: FC is disappearing overnight!

    Have you double checked the CYA result ?
    TFP Moderator
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    Re: FC is disappearing overnight!

    I have been keeping track of the CYA. We started the season with a O then after adding Stabilizer in a sock near the skimmer on 3 separate occassions it's got up to a 30 then 40 then 50. Will be checking everything again today as we got slammed with rain last night in the storms that went through the Midwest.
    12K AG, Vinyl Oval Pool, Swim Pro Sand Filter, Pentair Opti-Flo High Performance Pump-HP 2.0 SPL, New Vinyl liner June 2015

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