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Thread: FC not drifting down very fast

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    Join Date
    May 2013
    Needham, MA

    FC not drifting down very fast

    Second season with my pool. Normally I run a SWCG, but due to low water temps I have yet to turn on. Water is between 57-60 degrees. I opened the pool on April 13. Water was crystal clear, and still had a FC of 2.0 from last fall. The CC was 0.0. Water temp was 44. Laying on the side of caution I brought FC to slam level of 24. CYA is at 60, and for now I am treating it as a non-SWCG pool. Today when I tested my FC is at 14. I have yet to add any bleach since April 13. It has drifted only 10. I do have my solar cover on to catch debree, and to warm the water. Pool gets full sun from 12-5. I know this is a good thing, but can it be a bad thing for the FC to not drift down very fast? I have been testing every other day so I know today was not a bad test.
    14x28 Kidney IG vinyl pool, 9250 gallons. Pentair 1.5hp superflo variable speed, Pentair Clean and Clear 240 Cartridge filter, Pentair IC40 SWCG, Hayward Heatpro 110,000k heat pump, Pentair Intellibrite 5G LED lights, Polaris 280, Taylor K-2006 test kit

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    TFP Guide
    triptyx's Avatar
    Join Date
    Apr 2016
    Tucson, AZ

    Re: FC not drifting down very fast

    I'd actually say it's a good thing for the FC not to drift down very fast - that means there isn't a lot of nasties in your water for the chlorine to expend itself on.

    That said, if you're concerned about having something growing in the water, it's time to perform the OCLT test: Pool School - Perform the Overnight FC Loss Test (OCLT)

    If you pass that test, you can continue to let it fall to normal levels for your CYA and use bleach to maintain normal non-SWG levels until you get the water warm enough to fire up the generator.
    8,500gal plaster in-ground with attached spa, two floor drains, one skimmer. Chlorine, City Water.
    Pentair WhisperFlo 1hp Pump, MagnaTek Midcentury EPlus motor, Pentair CleanNClear 200SF Cartridge filter, Purex Triton MiniMax 250 Gas Heater, Pentair SunLite, AutoFill.
    Kreepy Krauly Cruiser, TF-100 with SpeedStir. :D

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    In the Industry

    Donldson's Avatar
    Join Date
    Jun 2009
    NW Ohio

    Re: FC not drifting down very fast

    Low temperature plus a covered pool makes for very low FC drop, perfectly normal. Like you said, you opened with 2 FC and how many months was that? No reason to worry in the slightest and certainly doesn't call for an OCLT, once your water warms up you will see more normal FC losses. But by then you will be able to turn on the SWG and start getting it dialed in for the season.
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath

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