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Thread: Salt Level Decreasing, Aeration a Factor?

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    john.esher's Avatar
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    Salt Level Decreasing, Aeration a Factor?

    My salinity has decreased today by 200 ppm over the last ten hours, measured this morning and just a few minutes ago. On Friday it was 3,000 and now I'm down to 2,600.

    I have been using muriatic acid over the last two days to lower my TA, and have been aerating all the while with the return jet breaking the surface to raise the pH. So I'm wondering if this is normal due to evaporation?

    (I have my SWG off as I recently started a SLAM, ran out of R-0871, and am in a holding pattern of nightly bleach additions.)
    Intex 18' x 52" AG with Sand Filter Pump & SWG (Model ECO15110) about 7,600 gallons tested with a K-2006-SALT.

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    Re: Salt Level Decreasing, Aeration a Factor?

    Salt doesn't evaporate. The only two explanations are testing error (either human or something is messing with your test) or you are losing a LOT of water. Unless you have an autofill then something must be causing a testing error.
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    Re: Salt Level Decreasing, Aeration a Factor?

    Quote Originally Posted by Donldson View Post
    or you are losing a LOT of water. Unless you have an autofill then something must be causing a testing error.
    No autofill, just a small Intex AG. And in my mind, losing water should not affect the ppm, just the volume in the pool, right? I haven't added any water in the last few days.

    Except, now that I type that, I did add some yesterday, so, duh, pay no attention to this post!


    Intex 18' x 52" AG with Sand Filter Pump & SWG (Model ECO15110) about 7,600 gallons tested with a K-2006-SALT.

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    Re: Salt Level Decreasing, Aeration a Factor?

    Quote Originally Posted by john.esher View Post
    My salinity has decreased today by 200 ppm over the last ten hours, measured this morning and just a few minutes ago. On Friday it was 3,000 and now I'm down to 2,600.
    Quote Originally Posted by Donldson View Post
    The only two explanations are testing error (either human or something is messing with your test) or you are losing a LOT of water.
    Another possible explanation would be a salt level of ~2800 ppm and a salt test with an accuracy of 200 ppm (or worse) ?
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    Re: Salt Level Decreasing, Aeration a Factor?

    Quote Originally Posted by john.esher View Post
    ........... And in my mind, losing water should not affect the ppm, just the volume in the pool, right?
    Losing water due to evaporation will raise the ppm concentration until you add replacement water.

    Losing water due to splashout/backwash/vacuum to waste will take salt with it. Replacing that water loss will dilute the salt, lowering the ppm concentration.

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    Re: Salt Level Decreasing, Aeration a Factor?

    Salt stays behind during evaporation. Removed during splash out /backwash. My guess test error.
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    Re: Salt Level Decreasing, Aeration a Factor?

    How did you test? That is only one drop in the Taylor test. And most tests and SWG are only good to +/-400ppm anyway.
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    Re: Salt Level Decreasing, Aeration a Factor?

    Into 10ml of water I put one drop of the yellow liquid (not in front of the bottles, so I don't know the numbers) and drop and swirl the other.

    Turns to a milky cream color then boom, salmon colored with a lot of things floating.

    Wasn't aware the +/- was so high.


    Intex 18' x 52" AG with Sand Filter Pump & SWG (Model ECO15110) about 7,600 gallons tested with a K-2006-SALT.

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    Re: Salt Level Decreasing, Aeration a Factor?

    I believe most test kits are that accurate.
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    Re: Salt Level Decreasing, Aeration a Factor?

    Quote Originally Posted by jblizzle View Post
    How did you test? That is only one drop in the Taylor test. And most tests and SWG are only good to +/-400ppm anyway.
    ^ This
    Most salt tests are only accurate to +/- 400 as Jason said, and it could vary a little more.
    As long as the generator is happy and making chlorine, its fine.
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    Re: Salt Level Decreasing, Aeration a Factor?

    If you use the Taylor K-1766 salt test, then using a 10 ml water sample it is +/- 200 ppm but if you use a 25 ml water sample it is +/- 80 ppm in terms of being +/- 1 drop in accuracy. However, overall the test is also limited by accuracy of the concentration of its reagents and your ability to measure volumes accurately and of drop size and all of these result in +/- 10% accuracy so at 3000 ppm that's +/- 300 ppm. For a given test kit, repeatability should be closer to the +/- 1 drop (if you do the test carefully), but absolute accuracy would be closer to the +/- 10%.
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