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Thread: Two quick questions re: free chlorine levels and how to test

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    Join Date
    Jan 2012
    Location
    Tucson AZ
    Posts
    18

    Two quick questions re: free chlorine levels and how to test

    I don't seem to be losing FC at a normal pace. Here in tucson the water's up to 60 degrees, I chlorinate with 10% liquid chlorine. I had a horrifying CYA level of 150, I managed to the get that down to 55 with a partial water change.

    However, despite the CYA being at a good level for here in AZ, my FC just doesn't seem to be changing much. I chlorinated on the 14th of February and brought the FC level up to 11, now on the 22nd, 8 days later, the FC has only dropped down to 9.5. The pool gets full-on sun all day so I really would've thought it would go down a lot more than that. Is FC loss dictated THAT much by temperature? I'm sure it's less in cold weather, but it's only 15-20 degrees lower than it will be in the summer.

    2nd question: With the taylor FAS-DPD test, or any titrating test for that matter, how important is it to swirl after each drop? Like, if you know the FC level is above say, 5, and you're doing the 10ml .5 per drop test, if you drop in like 5 at a time before swirling, is that going to completely wreck the test? I'm just thinking of reasons why I don't seem to be seeing a FC loss like I should be.
    15260 gal IG plaster pool
    Swimquip HRS16-01 Sand Filter (20-28 gpm)

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,083

    Re: Two quick questions re: free chlorine levels and how to

    is that going to completely wreck the test?
    No. While none of us advocate it, many of us (gulp ) will put in multiple drops at first and then swirl,,,,,knowing that the FC is going to test well above the initial # of drops put in.

    That darn Speedstir is a very helpful device to accurately perform those tests but the way you are doing should really have nothing to do with the accuracy of your result.

    I can't explain your minimal FC loss other than to say that temp REALLY has a big effect and, while yours is still less than I would expect, I would be very happy with the outcome. (sorta' like worrying about being too good looking or having too much money )
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Join Date
    Jan 2012
    Location
    Tucson AZ
    Posts
    18

    Re: Two quick questions re: free chlorine levels and how to

    Well, I guess we'll see. I've done the CYA test twice in case I screwed something up there, but the way that thing works, it seems like erring on the side of too high is far more likely than erring on the side of too low. So I know my CYA isn't the problem here. I guess I'll just enjoy the ride until it starts getting hotter, and see what it does then.
    15260 gal IG plaster pool
    Swimquip HRS16-01 Sand Filter (20-28 gpm)

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    Join Date
    Oct 2011
    Location
    New Caney, Texas
    Posts
    414

    Re: Two quick questions re: free chlorine levels and how to

    I'm still in the kid with a new toy mode so I test daily.

    On 2/5/2012 my FC was 1.5
    I added bleach.
    FC went to 6, it slowly fell to 1.5 on 2/20/2012. (15 days)

    My average water temp 58.59

    And got to love the Speedstir

    CYA is at 30
    18' x 42" Intex (4786 Gal @ 80% capacity) Intex 8110 SWCG, 2000 GPH cartridge filter.
    Full Sun, Well Water, Borates at approx. 50
    TFTestKit-100--The Pool Calculator--Pool School

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    Re: Two quick questions re: free chlorine levels and how to

    That sounds pretty close to what I'm seeing just a little north of you in Mesa. So nothing to worry about. Lack of use, shorter days, cooler temps, more cloud cover, denser air/less UV, etc. all add up to make a big difference.

    Pay attention though because during the summer you can easily use 1.5 FC or more in a day, not week! The change over is not as gradual as you might expect you can easily swing from one extreme to the other in a few weeks. Usually some time in May.
    Currently trying to decided what to build in the backyard in Phoenix.

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