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Thread: Overnight Free Chlorine Test

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    Overnight Free Chlorine Test

    When is the latest possible time you can test in the morning? A couple of minutes before "official sunrise?" I'm not an early riser and prefer to put it off as late as possible.

    Thanks,
    Alan

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    Mod Squad zea3's Avatar
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    Re: Overnight Free Chlorine Test

    As close to dawn as you can is best. If the sun has been up a couple of hours you have waited too long.
    TFP Moderator
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    Re: Overnight Free Chlorine Test

    the idea is to test it before sunlight starts affecting the FC... doesn't have to be "before" dawn, and can be a good bit later if fully shaded on the east!
    My pool doesn't start losing daytime FC until about 0800, but have 100 foot trees to the east...
    24ft x 52in AGP 18000 gal
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    Mod Squad Bama Rambler's Avatar
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    Re: Overnight Free Chlorine Test

    Just be aware that if you wait till the sun is up and you don't pass the test, you're gonna wonder if you really didn't pass it, or if it was just that you waited to long to test it. Personally, I'd rather get up a little earlier and be sure.
    Dave J. TFP Moderator
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    Re: Overnight Free Chlorine Test

    I'm still in the shocking phase and for the life of me can't figure out why I can't get Free Chlorine to hold overnight. My pool has looked great for the last couple of weeks and my CC's are below 1. Anyway, would it be unusual to lose 7-8 ppm per day at shock levels of 18-24 with a CYA of 40? I question whether or not I'm making any progress because I'm losing so much during the day. Is it possible that chlorine could drop that much due to sunlight at the higher shock levels?

    My current readings are:
    FC 18
    CC .5
    TC 18.5
    pH 7.6
    TA 100
    CYA 40

    Thanks,
    Alan
    17,500 Gallons
    Fiberglass
    Inground
    Sand Filter
    South Arkansas

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    Melt In The Sun's Avatar
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    Re: Overnight Free Chlorine Test

    Yes, that sounds very reasonable actually. The sunlight loss is why it's so important to do the overnight test, and yes, it must be early in the morning before the sun rises. You'll survive!
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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    Re: Overnight Free Chlorine Test

    For example, I raised my shock level to 21 early this morning and by 3:30 my level was 13. So you think this is reasonable with a CYA of 40 in South Arkansas?

    Thanks,
    Alan

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    Mod Squad zea3's Avatar
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    Re: Overnight Free Chlorine Test

    Be sure you check any nooks and crannies in your pool, removable ladders or hand rails, light niches, and skimmer openings. These spots can sometimes harbor algae and need to be brushed or spot treated to expose the algae to chlorine. The hidden algae will consume chlorine but the pool will look clear.
    TFP Moderator
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    At Wits End - Frustrated

    I am becoming very frustrated with this method but want to remain persistent. 3 WEEKS ago I took my pool cover off of my inground fiberglass pool. The water actually looked very clear. I started the dreaded shocking process and am still continuing to this day! What's even more frustrating is the fact that I lost 1 ppm on Wednesday night and 2 ppm last night. What kind of sense does that make? And I'm getting consistent readings with two consecutive tests each time I test. I've brushed my ladder with bleach and brushed the entire pool including skimmer opening and light several times during this process. From a clarity standpoint, the pool has looked about the same through the entire process. Does anyone have any logical suggestions as to where I should proceed from this point? I'm using the same CYA reagent that I used last year. Is it possible that the solution isn't any good and I have a higher CYA reading than I think...which would result in me shocking at lower levels than required? I don't know...I'm just trying to uncover any possible factors. Is it even logical that I would still be shocking for 3 WEEKS when my pool was covered over the winter and looked very clear when I opened? Do I need to change my testing process...let the chlorine drop to 7 or 8 and maybe get more accurate tests since I will be using fewer drops?? I have included pictures of some brownish-looking spots that have been in my pool for a couple of years that won't brush off. I'm not sure what they are but I doubt they are organic. I did want to post them just in case there's a slight chance they could be contributing to my problem...but I doubt it. Again, I'm just completely lost at this point and tired of getting up at dawn every morning.

    Thanks,
    Alan
    17,500 Gallons
    Inground
    Fiberglass
    Sand Filter
    South Arkansas


    Threads merged - MITS. Please keep your story all in one place; it makes it easier for everyone!

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    Re: At Wits End - Frustrated


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    crookm11's Avatar
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    Re: At Wits End - Frustrated

    What test kit are you using to test your pool? While shocking the pool are you maintaining the shock level during the process? I would suggest you read this topic on shocking a pool. How to Shock your Pool

    Please post a set of your pool numbers:

    FC:
    CC:
    PH:
    CH:
    TA:
    CYA:

    Mark Crook
    13,500 Gallon 24' x 52" Intex Ultra Frame
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  12. Back To Top    #12

    Re: At Wits End - Frustrated

    I've used this method for a couple of years and have read the site at least 25 times. I am maintaining shock level throughout the process. However, there may have been a couple of times throughout the 3 WEEKS that I let it fall below shock level...due to weather or being out of town. My readings are:

    FC 17
    CC .5
    TA 100
    CYA 40
    ph 7.6

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    Re: At Wits End - Frustrated

    Forgot to mention that I'm using TF-100 test kit.

  14. Back To Top    #14
    JasonLion's Avatar
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    Re: Overnight Free Chlorine Test

    Your numbers look good, and If I am following correctly the water is clear, and the overnight test has been only 1 ppm of chlorine lost on at least one night, and CC is 0.5 or lower, so it sounds like you are probably done shocking.

    The only questionable part is that you have had overnight losses of more than 1.0 on some nights. Is it possible that you are testing in the morning after the sun comes up? Or that the pump was not running for half an hour before both the evening and the morning tests?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  15. Back To Top    #15

    Re: Overnight Free Chlorine Test

    My pump is running 24 hours and I test every morning at 6:00 am...well before the sun comes up. And to clarify, I've never had 0 overnight FC loss...some nights it's 1 and others 2.

    Thanks,
    Alan

  16. Back To Top    #16
    JasonLion's Avatar
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    Re: Overnight Free Chlorine Test

    Are you using any sequestrant, or algaecide, or any other chemicals other than chlorine, in this pool?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  17. Back To Top    #17

    Re: Overnight Free Chlorine Test

    No other chemicals.

    Thanks,
    Alan

  18. Back To Top    #18

    Re: Overnight Free Chlorine Test

    Do you think it's possible that my CYA reagent from last year could've gone bad over the winter? Also, how much chlorine would you expect to lose from 6:00am to noon in South Arkansas on a bright, sunny day, if the chlorine level began at 25 at 6:00 am. I just checked and mine was 17. I've heard that it drops faster at higher levels, but that just seems like a lot. That's why I'm wondering about my CYA levels?? I measured the other day and got 40, but if the solution is bad maybe it's 20? Any ideas?

  19. Back To Top    #19

    Re: Overnight Free Chlorine Test

    Also, what about backwashing? I haven't backwashed in probably a week and a half because the pressure gauge has not indicated a need.

    Thanks,
    Alan

  20. Back To Top    #20
    JasonLion's Avatar
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    Re: Overnight Free Chlorine Test

    That is a perfectly reasonable FC loss during the morning, about 15%.

    Backwashing shouldn't affect it.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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