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Thread: UV and chlorine

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    ka8yiu's Avatar
    Join Date
    Aug 2016
    SW FL

    UV and chlorine

    I take it that the culprit during the day that causes the loss of chlorine is UV. Now in the south the UV is a year-round issue. However, the UV index may still max out lower in the winter months.

    So, has anyone with a year-round pool noticed a measurable decrease in the amount of chlorine lost in the winter vs. summer?
    8K gal IG Fiberglass (San Juan Waikiki I)
    TF-100 Testing Kit
    Hayward Max-Flo VS Pump
    Hayward Star Clear Plus Cartridge Filter
    Pentair Model 320 Automatic Chlorine/Bromine In-Line Feeder

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    Isaac-1's Avatar
    Join Date
    May 2010
    SW Louisiana

    Re: UV and chlorine

    There are other factors at play here, for one thing chlorine consumption greatly drops off with temperature decrease, this happens fairly dramaticly once the water goes below about 60F
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
    I use and endorse TFtestKits TF-100 from
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  3. Back To Top    #3
    Mod Squad
    Join Date
    Aug 2012
    DFW, TX

    Re: UV and chlorine

    +1 to that colder water, less sun, shorter days equals far less FC consumption.
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    JoyfulNoise's Avatar
    Join Date
    May 2015
    Tucson, AZ

    Re: UV and chlorine

    Short answer is yes. The sun is lower in the sky during winter months so there is a measurable drop in incident UV radiation. Temperatures are cooler and algae reproduction rates are insignificant below 60F.

    During the winter my SWG shuts off due to cold water. I typically use less than 3 gallons of bleach over 4 months.
    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, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

  5. Back To Top    #5

    Join Date
    Jul 2015
    Tempe, AZ

    Re: UV and chlorine

    Yes - far less FC use in the winter even here in AZ.

    In fact I got so complacent with it last winter, that in the spring when the days got a bit longer and we got a bit warmer, my pool took on a funny green color from the algae.
    John - 16,000 gallon | in ground | pebble | Triton II sand filter | TF100 | speedstir | Hayward Phoenix 2x

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