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Thread: At what point would a high FC become a problem?

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    Join Date
    Jun 2015
    Houston, Tx

    At what point would a high FC become a problem?

    I am in the middle of a SLAM and I am away from the pool for most of the day. How high can I crank up the FC before I have issues? My CYA is 30 so my goal FC is 12 but I know if I have it at 12 when I leave it will be too low by the time I get to put more bleach in. If I get the FC up to 20 I am asking for problems?
    In ground 30,000 gallon rectangular plaster/pebble pool, hot tub with blower, 2 HP Pentair WisperFlo Single Speed Pump, 420 Pentair Clean and Clear Plus Cartridge Filter, Pentair Rainbow 320 Chlorinator, Easy Touch Control System, Pentair 400K BTU heater, Interfab G Force Slide with dedicated 1 HP pump, Travertine Decking, CoverStar automatic pool cover

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    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    DFW, TX

    Re: At what point would a high FC become a problem?

    I think 15 would be a better place to start.
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    DaninFLA's Avatar
    Join Date
    Apr 2015
    Sarasota, FL

    Re: At what point would a high FC become a problem?

    i dont think 20 is going to matter esp since you have a plaster pool, besides its not going to stay there very long if you are dealing with algae. I did the same thing back in the day on my SLAM, i went a lot higher in the morning to try and keep the FC above the SLAM level for as long as i could. BUT, once your FC consumption starts to slow down, you dont need to go so high. start it at 20 in the morning, when you get home and re-measure to see how much you lost. if you are down to 4 or 5 then i would keep it at 20. if you come back and you are at 10, then dial it down to 15 to start
    9,000 gallon in-ground Saltwater pool, plaster, cartridge filer, 1.0 hp pump, Hayward T-15 SWCG, TF-100
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    JoyfulNoise's Avatar
    Join Date
    May 2015
    Tucson, AZ

    Re: At what point would a high FC become a problem?

    Consistent dosing is better than overdosing. Remember that, at shock levels, your FC/CYA ratio is already at 40%. That's more than sufficient to kill algae. The FC loss rate is directly proportional to the amount of active chlorine (hypochlorous acid and hypochlorite anion) in the pool water which is proportional to the FC/CYA ratio. So, at some point, if you just keep increasing the FC at constant CYA then all you're doing is wasting chlorine to sunlight loss.

    It would be better to find a way (ask a friend?) to keep the dosing consistent then to overshoot.

    One other way that might help would be to raise your CYA a little further. Yes, your shock level FC will increase but you'll lose less chlorine to sunlight and protect what you do put in the water for longer times.

    Ultimately it's up to you, but over doing the shock level is, ultimately, just wasting money.
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Join Date
    Jun 2015

    Re: At what point would a high FC become a problem?

    I kept mine at 16 for a week when slamming due to a mudslide with a CYA of 30. No issues.
    18' x 38' Pool, 3' to 8' Depth
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