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Thread: FC Testing of Cold Water (55o F)

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    FC Testing of Cold Water (55o F)

    As the water has gotten colder around here, I've noticed something weird when I do a FC test - particularly in a pool with a higher FC level (5+)...

    The sample doesn't go "pink" as fast, so I wait... then after I drop-test the water goes clear. Then, 30 seconds later, it is a light pink... again. Add a drop or two of test solution, goes clear right away and then (depending on FC), goes light pink again.

    Anyone else seen this?

    Thanks.

    - Jeff
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
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    Re: FC Testing of Cold Water (55o F)

    As chem geek has posted before, everything slows down at colder temps. (sugar dissolves more slowly in colder water than warm).

    As for the return to pink after the solution has cleared, that is perfectly normal and occurs regardless of the temperature. Disregard it. Once you have cleared the solution (endpoint), the test is completed.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Mod Squad Bama Rambler's Avatar
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    Re: FC Testing of Cold Water (55o F)

    All I can do is agree with Daves post. I've seen it do the same thing on my tests. Now I pour out the sample as soon as I'm done. That way it doesn't bother me to look at it. outta sight, outta mind!
    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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    Re: FC Testing of Cold Water (55o F)

    Quote Originally Posted by duraleigh
    As chem geek has posted before, everything slows down at colder temps. (sugar dissolves more slowly in colder water than warm).

    As for the return to pink after the solution has cleared, that is perfectly normal and occurs regardless of the temperature. Disregard it. Once you have cleared the solution (endpoint), the test is completed.

    But I've never seen it return to pink when the water is warmer... and I test a LOT of water.
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
    Pumps: X3 Hybrid Pump (switches to SPA), 2HP Spa (additional, when SPA is on), and a 1HP For Waterfall
    8, 4x12 Solar Panels on the roof of the pool-house (~12' up)
    CAPTAIN JAMES T. KIRK: "I'M SORRY. I CAN'T HEAR YOU OVER THE SOUND OF HOW AWESOME I AM" (Thanks to TFP!)

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    Join Date
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    Re: FC Testing of Cold Water (55o F)

    Well, try some experiments. Get your sample, then cup your hands around it for a minute to warm it up some... then test. Then run a second test letting it sit for the same length of time without warming up. See what happens.

    In my own pool, sometimes I get the late-stage pink and sometimes not. I haven't noticed any particular pattern to it (but then I haven't been looking for one).

    Another thing to remember is that with water temps now very low (mine was 52F today) the FC is less critical than during the summer.
    --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
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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