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Thread: FC Loss overnight

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    Join Date
    May 2013
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    FC Loss overnight

    Morning everyone. Is this something that should concern me? My FC last night was 3.5 and CC 0, this morning the FC was at 2.5 and CC at .5. The CC was within limits but I lost chlorine overnight. Do you think this something to be concerned about or is this normal? I added more bleach this morning to put at a FC of 5 (My CYA should be around 40, it was added as the pool was filling 2 days ago).

    Thanks everyone!
    24' Round AGP, 13,500 Gallons. 19" Ecco Sand Filter, 1.5 HP ecco pump.

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    Charlie_R's Avatar
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    Re: FC Loss overnight

    Was there anyone swimming yesterday evening before your test?

    That is actually pretty normal. Some organics take a bit of time to be oxidized, so will show up like that.
    15'x48" 4500 gallon Intex pool, buried 1.5 ft. Pac-Fab Dynamo 3/4 hp pump. Hayward S180T sand filter, bought used. Taylor K-2006 test kit. Rocket mass heater based wood fired pool heater.

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    duraleigh's Avatar
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    Re: FC Loss overnight

    A 1.0 loss of FC overnight is acceptable. Anything greater indicates the need to SLAM the pool.

    You're OK except I would keep FC a tad bit higher so you don't go below the minimum of 3 ppm/CYA 40
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: FC Loss overnight

    Quote Originally Posted by Charlie_R
    Was there anyone swimming yesterday evening before your test?

    That is actually pretty normal. Some organics take a bit of time to be oxidized, so will show up like that.
    We were in the pool all day long right up until about a half hour before I tested it.

    I did add enough bleach this morning to get back up to 5 FC.
    24' Round AGP, 13,500 Gallons. 19" Ecco Sand Filter, 1.5 HP ecco pump.

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    pwrstrk's Avatar
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    Re: FC Loss overnight

    That's prob where you lost .5ppm. Not a big deal. You might want to shoot a tad higher in FC range if you get alot of sun and use.


    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    BoDarville's Avatar
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    Re: FC Loss overnight

    You're good to go, as the others have stated. Worth reinforcing what others have said...FC should be increased a bit to allow for loss due to sunlight and normal disinfection. At a CYA of 40, you never want FC going below 3 ppm at any time. Recommend dosing chlorine in the evening after no more sunlight is hitting the pool. Try dosing FC to the mid-point of the recommended range (5 ppm) for a CYA of 40 to give you some headroom for normal daily FC loss.
    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
    A good test kit is an investment, not an expense.

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