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Thread: total chlorine vs free chlorine

  1. #1
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    Default total chlorine vs free chlorine

    Having an issue with clear water. Everything seemed right-on with the test.....but:
    pH 7.6
    TA 105
    CYA 33
    Free Chlorine 0
    Total Chlorine 7.5

    I added soda ash to bump the pH from 6.8 to 7.6. Did its job, but, water got cloudy and is clearing over past 2 days since the baking soda, but still fairly cloudy.

    Any suggestions on what I can do to get TC and FC closer? (assuming that's the cause of the cloudiness).

    Thanks.

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    Default Re: total chlorine vs free chlorine

    Soda Ash, Baking Soda?
    FC 0 - Pool needs more chlorine, no FC and it'll turn green.
    I suggest bleach and a review of the stickies in the Using Chlorine and Chlorinating Chemicals forum.
    How are you testing?
    12'x24' oval 7.7K gal AG vinyl pool; ; Hayward S270T sand filter; Hayward EcoStar SP3400VSP pump; hrs; K-2006; PF:16

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    Default Re: total chlorine vs free chlorine

    Soda Ash.
    I have a Taylor K-2006 on order.
    Current testing was done at local pool store. Their advise was to shutdown the chlorinator until TC comes down. And that's what I don't get. Water is still pretty cold, but not too cold for algae.
    Have been running Hayward chlorinator with 3" disks on full blast for past few days. Is definitely dissolving/absorving the disks. I don't understand why it isn't "taking hold" and getting the FC level up to a decent level?
    Trouble is my pool is big.....50K gal big. So, if I go with bleach....how much and how often until I can expect chlorinator and disks to kick-in and do their thing?
    Thanks for advice.......

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    Default Re: total chlorine vs free chlorine

    How are you testing?

    The results you have ("33", "105") are characteristic of some sort of digital test reader. Unfortunately, these range from somewhat inaccurate, to wildly inaccurate. Drop count tests, like the HTH 6-way kit from Walmart or the Taylor K2006, are more accurate, and much more reliable, but give less precise numbers ("30", "110").

    However . . . . cloudiness immediately after adding soda ash is almost certainly precipitated calcium. I can't be 100% sure, since you didn't report calcium levels, but it's still quite likely that calcium is the issue.

    TC vs FC -- depends on how you are testing. If you test results are accurate, then you likely have high TC levels EITHER because you've used some algaecides or other products that react badly with chlorine OR, because you have missing stabilizer. This page ( http://www.poolforum.com/pf2/showthread.php?16973 ) how to do a bucket test to figure out what it will take to fix the problem.

    Oops, we posted simulaneously! DEFINITELY, do the bucket test. That will answer the "how much" and "how long" questions you have. If you've converted 50ppm of stabilizer to ammonia, the answers will be (unfortunately) "a lot" and "a long time".

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    Default Re: total chlorine vs free chlorine

    Will review the "bucket test" and do it. CYA is same as "stabilizer", right? Mine was 33....which looks to be low but still within "normal" range? I don't have a Ca++ category on the water test....but Total Hardness is 163 (normal 175-225 acc to sheet). Aren't they related?

    Thanks for the help.

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    Default Re: total chlorine vs free chlorine

    CYA = cyanuric acid = stabilizer

    33 ppm is OK, but low in most cases. However, I don't trust the reading -- the actual accuracy of test strip reading for CYA is +/-30 ppm OR worse! Your actual CYA might be anything from 0 ppm to 60 ppm!

    Total hardness = Ca + Mg => but on most pools, it's 90+% Ca (Ca = calcium; Mg = magnesium). And, Mg doesn't cloud the water when you add soda ash!

    BTW, your bucket test results for chlorine demand won't be too accurate, till you have the K2006. There are work-arounds, but they are tricky.

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    Default Re: total chlorine vs free chlorine

    Here's my concern.....the bucket test looks like it takes a couple of days to fully complete. I can start on that tomorrow after getting the ingredients. BUT....I don't want a green pool, since I've shut down the chlorinator (per advice of the pool store guy). In an effort to head off an algae bloom, would you recommend that I kick the chlorinator back on high and then add some amount of Bleach??.....in an effort to get a registered amount of Free Chlorine. Any guide on how much bleach?

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    Default Re: total chlorine vs free chlorine

    In reading around.....I've read several recommendations for "non-chlorine shock" in order to oxidize and free-up the bound chlorine....and break the "chlorine lock" that I apparently have. Any thoughts on this?

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    Default Re: total chlorine vs free chlorine

    I don't think that will help and it will be a lot more expensive than chlorinating liquid or bleach. You need to shock your pool with chlorine and keep adding it until you start registering an FC level. You may have a lot of ammonia in your pool, though normally that comes from a breakdown of CYA by bacteria. Did you just open your pool and find this problem? If so, then that may be what happened, though all the CYA didn't get converted since you still measure some.
    15.5'x32' rectangle 16K gal IG concrete pool; 12.5% chlorinating liquid by hand; Jandy CL340 cartridge filter; Pentair Intelliflo VF pump; 8hrs; Taylor K-2006 and TFTestkits TF-100; utility water; summer: automatic; winter: automatic; ; PF:7.5

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    Default Re: total chlorine vs free chlorine

    => The chlorine demand bucket test doesn't take a couple of days. A matter of hours should be enough. It *will* require a K2006 or equiv for meaningful results.

    => If you raise the pH above 7.6, and continue to maintain high levels of CC, the CC will gradually take the form of monochloramine, which is a very effective algicide. But, you don't want to swim in 7.5 ppm of monochloramine -- it will severely irritate your eyes, and possibly, your skin.

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