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Thread: Unexpected high FC levels question

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    Join Date
    May 2007
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    Fayetteville, Arkansas
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    Unexpected high FC levels question

    What could cause my FC number to still register high after brushing the entire pool. I applied the initial dose of bleach to the specified shock level, rechecked and brought it back up to shock. Now the last few times I've checked it the FC level is very hot pink (high). It appears there is no consumption of FC. Combined is < 1ppm.

    CYA 50
    Ph 7.2
    TA 60

    Ideas?
    20x40 30,000 gal IG Liner, Pentair II Sand

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    Re: Unexpected high FC levels question

    Not clear what you mean by hot pink--do you have the FAS-DPD test, or just DPD?
    Have you done the overnight loss test? How does the water look?
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
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    Water testing instructions on one page

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    Re: Unexpected high FC levels question

    I have the FAS-DPD kit and the two scoops of 870 turn the sample hot pink as in lots of FC in the water. Over night test shows no loss which is weird and the water is clearing. Still lots of algae on the floor and side walls which is typical at opening. I started the opening/clearing process two days ago.
    20x40 30,000 gal IG Liner, Pentair II Sand

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    Re: Unexpected high FC levels question

    Not to ask a dumb question, and kick me if you want
    But..you are titrating the pink color to clear with the 871 reagent, correct?
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Unexpected high FC levels question

    yes and getting near shock level on the count ... that's what the mystery is.
    20x40 30,000 gal IG Liner, Pentair II Sand

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    Mod Squad Bama Rambler's Avatar
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    Re: Unexpected high FC levels question

    Please post a full set of numbers. It'll help us understand what's going on and how to help you.
    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
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    Ohm_Boy's Avatar
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    Re: Unexpected high FC levels question

    I'm confused. In two days, you raised FC to shock level, topped it off to shock level, and are testing at shock level? Is that the problem?
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

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    JasonLion's Avatar
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    Re: Unexpected high FC levels question

    The intensity of the pink color you get after adding R-0870 doesn't tell you what the FC level is. You need to count the number of drops of R-0871 that it takes to turn the sample clear.

    I very much doubt that your FC level is still exactly the same as what it was. On the other hand, it is perfectly plausible that your FC level is still very high. With CYA around 50 you are going to lose between 40% and 60% of your FC level every 24 hours. If FC started at say 20, it could easily still be 10 or even 15, both of which are high.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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