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Thread: Calcium Hardness testing question

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    Calcium Hardness testing question

    Hi there,

    Question on how to read the Taylor K-2006 test kit for Calcium Hardness.

    We have well water and no softener. When I read the CH I'm getting about 120 - 140 for when the color goes from red to blue, but there's still pink floaters in it. When the spa company reads a sample they're in the 200 - 230 range. The instructions with the test kit say stop titrating when the color goes from red to blue overall and disregard any pink floaters. Does that mean there should be no pink floaters when you're done? If so, that seems to happen at the higher range, closer to what the store reads the CH as on their computer. And how blue is blue? It goes through a bit of a purplish phase at about 100 and then an extra 2 - 4 drops take it to what I'd call blue.

    The other thought I had was the store print out is saying "Hardness" not "Total Hardness" so I assumed it's just CH but maybe I shouldn't. Is it possible they're reading TH and my test kit is reading CH and both are right? But I didn't think we cared about magnesium hardness in spas so I would think they're Hardness is CH only but it was just a thought I had.

    thanks!

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    JasonLion's Avatar
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    Re: Calcium Hardness testing question

    You add drops until it turns to something in the blue family, then you continue adding drops as long as the color continues to change. The final drop, which doesn't change the color any further does not count.

    On the CH test, you need watch out for purple. Purple is a fading endpoint, and can cause a false high reading. If you see purple, see if additional swirling clears it up before adding more drops. A speed stir helps with this.

    Don't assume that spa company is correct. It is rather more likely that your result is correct.

    If the spa people use a drop based test or a fancy setup with a computer, a machine, and a syringe to add liquid, then it is calcium hardness. But if they are using test strips, with or without a machine, then it is total hardness.
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    Re: Calcium Hardness testing question

    Ok thanks for clearing that up. We are reading it low then with our test kit because we still have changes but it's all in the blue family so we'll take it until no more change next week. The store is testing CH then since they take our water sample and use a syringe to put it into the machine that the computer reads. We have some Insta test strips and that says TH (has 250 - 400 as the "ok" range).

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    Re: Calcium Hardness testing question

    As described in Extended Test Kit Directions:

    The sample may turn purple during the test, or go to blue for a moment and then turn back to red/pink. This is called a "fading endpoint" and is caused by interference from metal ions. If this happens, do the test again, but this time add five drops of R-0012 before adding any R-0010 or R-0011L. Remember to count the initial five drops in the total.
    In extreme cases, a fading endpoint may occur even when adding five drops of R-0012 at the start. If that happens, mix pool water with an equal quantity of distilled water, test that, and then multiply the result by two.
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    Re: Calcium Hardness testing question

    Yeah I don't have it go blue and then back, it's just as it's changing from red to blue it sorta looks a bit purple with the red floaters. I like the description of "add until it doesn't change anymore and don't count the last drop". I think that will account for me reading it low vs the store by about 60 - 90ppm. Given we're on well water I always thought it was odd we were on the very low end of the range.

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    Re: Calcium Hardness testing question

    Following the extended instructions and using a speedstir would probably help you get more accurate and precise readings.

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    Re: Calcium Hardness testing question

    Quote Originally Posted by JamesW View Post
    Following the extended instructions and using a speedstir would probably help you get more accurate and precise readings.
    I'm thinking since it's just a home use thing, maybe I won't go that far. If I want it really exact, I can always take a sample every few weeks down to the store since my husband works not far from there.

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    Re: Calcium Hardness testing question

    my 2 ct's. Get the speedstir. Makes testing so much easier
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    gtemkin's Avatar
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    Re: Calcium Hardness testing question

    Quote Originally Posted by edwin2014 View Post
    my 2 ct's. Get the speedstir. Makes testing so much easier
    Agreed....especially for that test.
    21K gal 16' x 40' in-ground pool built 1959, old school with Jacuzzi bronze pump, American Products 24" Sand Filter & Americana Multiport valve, Jandy Lite2 millivolt heater, Coverstar cover, and classic Kreepy Krauly.

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