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Thread: Alk test is blue, calcium test is clear, explain?

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    Alk test is blue, calcium test is clear, explain?

    Hi All
    I am trying to balance pool water. Tested the pool with test kit.
    PH 7.3
    Alk ? Fluid is blue added drops no change
    Cal ? Clear, added drops still clear
    Bromine 10

    Gallons: 32,000

    Not sure if the pool has a high Alk, what does it mean when the reagent turn blue. What does it mean when the calcium is clear.

    Cat 2000 controller is showing a fluctuating PH

    Thanks
    James

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    JasonLion's Avatar
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    Re: Alk test is blue, calcium test is clear, explain?

    That usually means the FC level is really high and is bleaching out, or partially bleaching out, the indicator dye for the tests. You can usually still do the TA and CH tests, but the color change you are looking for changes.

    See the Extended Test Kit Directions for more info.

    By the by, FC high enough to bleach out the TA and CH tests is usually high enough to completely invalidate the PH test as well.

    Best to figure out the FC level and get it back under control before worrying too much about the PH probe being inconsistent. Various problems, from fouling to bad circulation in the probe test cell, could have affected both of the sensors there
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Alk test is blue, calcium test is clear, explain?

    It is a chlorine pool and not a bromine pool....correct?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Alk test is blue, calcium test is clear, explain?

    Very good Jason, I will follow up with the results. Thank you!

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    Patrick_B's Avatar
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    Re: Alk test is blue, calcium test is clear, explain?

    If the TA turns blue, it's FC. Make sure you added Sodium Thiosulfate to it when you start. In a Taylor kit that's R0007 and it neutralizes/scavenges the FC. The result is the same even if you don't, but it's end point will be yellow instead of pink/red.
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