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Thread: Free chlorine endpoint?

  1. Back To Top    #1

    Join Date
    Jun 2014
    Location
    pendleton,IN
    Posts
    15

    Free chlorine endpoint?

    While using your test kit for free and combined chlorine i observed some turbidity indicating a precipitate instead of a clear solution when the initial titration for free cl was reached. Within a few seconds a faint pink color returns and keeps returning for several additonal drops. For example , the initial titration may be 4 to six drops and subsequent titrations may be as high as an additional 4 to six drops. I still have a relative high amount of combined chlorine and my ca level is around 500 due to well water. Do either one of these conditions interfer with the analysis? Could the precipitate be a reaction taking place because of a ph change ? I am basing my adds more on the initial endpoint and also the fact that i still have a relative high level of combined chlorine. The water is clear and very warm due to ambient temp. And automatic cover. My biggest problem was from over stabilization due to high cya which is down to the 10 to 20 range since started slamming with bleach and discontinued the use of chlorine tablets through a auto feeeder. Thanks to your forum i have eliminated white water mold and pink slime for now. My pool has problems similar to a hot tub since it is covered and warm a good deal of the time. My wife and are retired and use it for low impact aerobics and pool walking for fibromyalgia and arthritus along back problems so we have a shallow pool with a vinyl cover. I run the sand filter 24/7 which is slightly oversized along with a 1 horse pump. I also have a natural gas heater. Equipement is hayward. Location is central indiana.
    THE ENDPOINT TURNS BACK ALMOST IMMEDIATELY THEN GRADUALLY INCREASES WITH TIME FROM A FEW SECONDS TO TEN OR FIFTEEN SECONDS ALONG WITH TURBIDITY WHICH IN MY EXPERIENCE INDICATES BACKGROUND INTERFERENCE. THE TURBIDITY IS LESS THAN 20 ON THE SCALE SO I AM GUESSING IT IS IN THE 10 TO 20 RANGE. I HAVE DECANTED THE POOL THROUGH FREQUENT BACKWASHING AND A WINTER LOSS FROM NOT REMOVING WATER FROM POOL COVER -WE GO SOUTH IN WINTER-AND PUSHING IT OUT THROUGH SKIMMER. I HAVE ALWAYS RUN MY PUMP 24/7 WITH BOTH POOLS SINCE THE SAND FILTER IS SO INEFFICIENT AND I USE A HEATER. I ALSO HAVE A FLOATING AUTO COVER IN A BACKYARD FULL OF TREE AND GARDENS CLOSE BY. ADDING CHLORINE DAILY NEEDS CIRCULATION ESPECIALLY SINCE I HAVE A WHITE WATER MOLD PROBLEM IN THE PIPIING. I USE THE INITIAL ENDPOINT AS MY READING. CYA<20,CA=500,FREE CL 2T05, COMBINED CL 2TO5, ALKALINITY 100, PH 7.4-7.6. BEFORE DILUTION MY CYA WAS AROUND 60TO80. I HAVE READ YOUR POOL SCHOOL WHICH IS WHY I BEGAN USING BLEACH INSTEAD OF STABILIZED CL. CAPTURING RAIN WATER IS AN INTERESTING IDEA, THANKS FOR THE TIP. IWAS CONSIDERING HAVING WATER TRUCKED IN FOR A DECANT, EVENTUALLY.
    2007 16Xyward32 vinyl pool , deep end only 5ft. about 15000 gal,all hayward equipement, filter s244s pro series side mount sand filter,1horse single speed super pump ,model H250DL2 natural gas heater,automatic pool cover,automatic cl feeder not currently in use

  2. Back To Top    #2

    Join Date
    May 2014
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    Current: Singapore Previous: Clayton, Victoria, Australia
    Posts
    584

    Re: Free chlorine endpoint?

    If you leave the FC/CC test standing for long enough, it will turn pink on its own. The reading is taken the first time the colour changes.
    CH of 500 is very high, since you are on a well I would advise harvesting rainwater to reduce your CYA level.
    How do you know your CYA is 10-20? None of the recommended test kits gives that range out of the box.
    Additionally, SLAMming the pool and discontinuing the use of tablets do not normally bring CYA levels down significantly.

    Can you please post full test results?

    I would also advise that you read Pool School, in particular ABCs of pool water chemistry if you haven't already done so.

  3. Back To Top    #3
    Patrick_B's Avatar
    Join Date
    Jun 2011
    Location
    Midland TX
    Posts
    15,001

    Re: Free chlorine endpoint?

    Hi Eaglehawk, and welcome to TFP.

    Once you titrate to clear, that is your result, so don't worry about it turning back.

    I would suggest letting your pool get some sunlight during all the warm days whenever possible. UV exposure will help break down the CC and get rid of them. I too am curious how you arrived at the Cya 10-20, so please let us know more about that.

    Do you have a timer on the pool pump? If so, once you know you are completely out of SLAM territory, you should easily be able to cut that run time in half. Perhaps more since you are covered and have that option to help keep the pool even cleaner on windy days etc.
    TFP Moderator
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