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Thread: Different numbers on my test kit?

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    Different numbers on my test kit?

    My concern is two-fold.

    1. I bought a little test kit that came with 2 bottles to test ph and chlorine. The acrylic vials have numbers next to them and that typical color bar and I'm to add 5 drops of the appropriate reagent to each side. The ph side makes sense, but the chlorine side has a different scale. It has .5, 1.0, etc. up to 5.0, and it says "ideal" is 1.0 to 1.5, which is a very pale yellow. 5 is a dark yellow. Is their version of test tube different than everyone else'? It's appearing to me that if these numbers are ppm like they say they are, then I have very little chrlorine in here, but I don't know how to get it to the off-the-chart 6 ppm. 'Anyone else have this issue?

    2. When I first filled my pool, the test read between 7.8 and 8.2 for ph and in the "ideal" range for chlorine. I dutifully began the 4 day start up by adding what was to be a total of 14 oz of dichlor (I used the pool calculator, hopefully correctly), only on the third day I realized I was not using dichlor, I was using algaecide 60, silly me. Now my readings are the same for ph and if it's even possible, less than .5 for chlorine. It's totally clear on that side.

    The test kit says the chlorine side reads FC after 10 seconds and total chlorine after 2 minutes and if there's a discrepancy of more than 1.0, it's reading false chlorine and that I'll have to shock it.

    What do y'all think?
    12' x 36" Intex AGP on a raised concrete slab under a ramada in sunny Arizona. Borated, balanced, and beautiful blue.

  2. Back To Top    #2
    JasonLion's Avatar
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    Re: Different numbers on my test kit?

    1) That sounds like a fairly standard OTO chlorine test. Most of us use the FAS-DPD chlorine test, which is much more flexible and precise, but OTO chlorine tests are common enough. The OTO chlorine test measures TC (FC+CC) from 0 to 5, though most people can't distinguish between anything between 3 and 12.

    Their claim of reading FC at first and CC after a while is sort of mostly true. In practice most people can't reliably distinguish the two readings. You have to be very good at matching shades of yellow very quickly to get a meaningful FC readings, because it starts shifting towards the TC reading rather quickly, especially when CC is high.

    2) Your FC level is going to be zero at this point. Without CYA you lose all of your chlorine over one sunny day.

    As long as your water is still clear there is no real problem. Just start doing the regular startup process now. Longer term I recommend getting a FAS-DPD chlorine test.
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    Mod Squad Bama Rambler's Avatar
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    Re: Different numbers on my test kit?

    I think you need a better test kit! Seriously, that kit is probably fine for pH but the chlorine test is probably not going to cut it.

    1) You can get it 'off the chart' by adding more chlorine to the pool. You can use the Pool Calc to figure how much FC to add.

    2) It is not only possible, but definitely less than .5 if all you've added is algaecide. You need to start the 4-day startup again and forget the previous attempt. This time use Dichlor!

    Jason beat me to it but we're on the same page.
    Dave J. TFP Moderator
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    Re: Different numbers on my test kit?

    Thank you for responding SO QUICKLY, but how is it that "ideal" to them is 1.0 to 1.5?
    12' x 36" Intex AGP on a raised concrete slab under a ramada in sunny Arizona. Borated, balanced, and beautiful blue.

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    Isaac-1's Avatar
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    Re: Different numbers on my test kit?

    I am with the others, you need a better test kit, the basic OTO kit has its place, it works great for daily pool testing if your CYA level is below about 40, and you have the fancier FAS-DPD chlorine test to run once or twice per week. It is also OK for a small pool where you can easily dump the water and start over.


    Ike

    p.s. that "ideal range" is assuming you have no CYA, this has been the "ideal" range listed on pool test products for 40+ years, a lot of the pool industry does not account for the CYA chlorine relationship, although we have seen signs of its acceptance picking up in the last few years.
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    Re: Different numbers on my test kit?

    Just to clarify, and to make sure I'm on the absolute right track:

    1. In the evening, after I add muriatic acid to lower the ph (if necessary), a half an hour later I'm adding dichlor at the rate of about 3 oz/night for 4 nights. Out of the many choices of shock I looked at, I bought the one that is sodium dichloro-s-triazinetrione 58.2% with 41.8% other ingredients. That was the only one that didn't have copper as an ingredient or had trichlorxxxxx something as it's main ingredient. Was this the right stuff?
    2. I'm to buy a CYA test kit and watch for the black dot. I thought I'd try this after the 3rd night, as the pool calculator says I should add 9.6 oz.
    3. I should buy the fancier test kit eventually to monitor my various chlorines.
    4. Based on reading, I'm safe to float in it this afternoon?

    Thank you. All this is overwhelming, yet as I absorb it, it is starting to make sense.

    p.s. One last thing. As this is under a ramada, it doesn't get boatloads of sun. Is it direct sunlight that eats chlorine or does ambient, if that's the correct word, sunshine do as much robbery?
    12' x 36" Intex AGP on a raised concrete slab under a ramada in sunny Arizona. Borated, balanced, and beautiful blue.

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    Isaac-1's Avatar
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    Re: Different numbers on my test kit?

    Ok, assuming that you are working form a fresh fill, you can use dichlor, trichlor, and / or CYA stabilizer to build up your CYA level, you just need to keep careful track of how much you add, you can use pool calculator to keep track of the effects. Dichlor and trichlor will add both Chlorine and CYA (they are also both slightly acidic), assuming a target CYA level of 40 you will need to add a TOTAL of 26 ounces of Dichlor to reach a CYA level of 40. The best way to do this is about 2 or 3 oz at a time testing to make sure your FC level stays below 5 ppm on your OTO test kit. (I would start off 2 oz at a time for the first several days, then move up to 3 oz as you build up some CYA). After that you will want to switch to liquid chlorine or bleach to avoid getting your CYA too high, and maintain an FC level of between 4 and 5 ppm on your OTO test kit.


    (if your going to use both trichlor and dichlor the math gets more complicated, but the theory is the same)

    Ike

    p.s. while your building up CYA you probably want to target 3 - 3.5 ppm for your FC level, maybe a little less the first few days
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
    I use and endorse TFtestKits TF-100 from http://tftestkits.net
    ~Remember TFP counts on your donations to keep this site ad free~

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