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Thread: pH is purple!

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    tlwilson's Avatar
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    pH is purple!

    Realize now pH reads high when chlorine is high. Please disregard.
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    pwrstrk's Avatar
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    Re: pH is purple!

    Yep at FC levels of 10 or more. Good catch ! 😎
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Re: pH is purple!

    I can still read pH with high chlorine levels. Im sure theres a greater +/- accuracy percentage. Also I have never done it when the pH was off the scale which yours could be because Ive never seen the color purple.
    You have to hurry to do it which isnt that hard to do.
    When you put the 5 drops phenol red, hurry and cap it, invert it about 4 times to mix, hold it to the sky and the first color you see is the pH. If you stand there trying to compare colors then you can see the color changing so dont second guess yourself.
    18,000 Gallon Aboveground. Sand Filter with 2HP 2 speed Pump.

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    Re: pH is purple!

    When you put the 5 drops phenol red, hurry and cap it, invert it about 4 times to mix, hold it to the sky and the first color you see is the pH.
    I have never noticed that. As soon as I begin to mix the reagent, it seems to immediately go to it's final shade with no more variation....certainly not enough time for me to take a pre-reading.

    How long would you guess you have before the solution starts to turn?

    Are you using Taylor or another brand reagent?
    Dave S.
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    Re: pH is purple!

    Quote Originally Posted by duraleigh View Post
    I have never noticed that. As soon as I begin to mix the reagent, it seems to immediately go to it's final shade with no more variation....certainly not enough time for me to take a pre-reading.

    How long would you guess you have before the solution starts to turn?

    Are you using Taylor or another brand reagent?
    I would guess it starts to turn as soon as the drops are added and before mixing. Thats why I hurry. Ive done it at shock level a bunch of times with new reagent and old. Do I know its 100% accurate? No, but it does seem to be. As soon as I put 5 drops phenol red, cap it, invert it a few times to mix and then look, I can see it changing colors. Thats why its the first color shade you see. I do suppose the first shade you see could be 0.2 higher than actual just because of the second it takes to cap it and invert it to mix. The higher the chlorine level, the faster it will turn shades. I usually keep my ph between 7.4 and 7.6 so I havent any experience with 8.0 and above which is why I assume his shade turns to purple.

    I use the Aqua Chem brand pH/chlorine tester from Walmart.
    http://www.walmart.com/ip/Aqua-Chemi...t-Kit/17126394

    However I just got the tft100 test kit a few weeks ago with the taylor pH test kit. I just slammed my pool last week and If my memory is correct I used both pH testers to check the pH level while chlorine was high just to compare the two and they both done the same thing. My chlorine has come down to normal levels now so I cant run out there and check the taylor kit.
    18,000 Gallon Aboveground. Sand Filter with 2HP 2 speed Pump.

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    Re: pH is purple!

    I failed to say that sometimes I also do not read it quick enough just like you duraleigh. Sometimes I have to do it twice but always have read it as far as I can remember. You have to go as fast as physically possible to do it. That means hurry and sit the bottle of phenol red down and cap it along with the rest.

    If you try it, let me know what happens. I dont know why it would work for me and not anyone else.
    18,000 Gallon Aboveground. Sand Filter with 2HP 2 speed Pump.

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    Re: pH is purple!

    Well I closed the pool and raised the FC. I decided to check my pH after and now it doesnt work like I said it would. I tried the aqua chem pH tester and the taylor pH tester. Same thing. It immediately went to deep red. I believe you jinxed me Duraleigh. I was in a hurry and actually added too much chlorine for my CYA (slam level). I wonder if thats why. I know I have done it many times but I dont remember exactly what the chlorine level was but I know it was around shock levels. I am going to find out but it will be next year some time.
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    Re: pH is purple!

    Quote Originally Posted by easttn View Post
    I can still read pH with high chlorine levels. Im sure theres a greater +/- accuracy percentage. Also I have never done it when the pH was off the scale which yours could be because Ive never seen the color purple.
    You have to hurry to do it which isnt that hard to do.
    When you put the 5 drops phenol red, hurry and cap it, invert it about 4 times to mix, hold it to the sky and the first color you see is the pH. If you stand there trying to compare colors then you can see the color changing so dont second guess yourself.
    High FC interferes with the pH test (Phenol Red method) PERIOD.

    You are not getting accurate pH with high FC levels so those new to testing please make note of that. Do NOT make pH adjustments based on Phenol Red pH tests when you have high FC levels, such as when SLAMing


    As far as this test changing colors, I have never seen this. You mix the test sample, then judge colors and take the reading.
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    Re: pH is purple!

    I guess its going to be like a Bigfoot sighting. "I know what I saw" but everyone else will think your crazy. I knew I shouldnt have said anything about it. I guess I will continue doing the impossible.
    18,000 Gallon Aboveground. Sand Filter with 2HP 2 speed Pump.

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    Re: pH is purple!

    I have seen this happen when the fc is over 10 ppm, but less than 15% of the CYA. I have seen the delay from a few seconds to several minutes.

    The lower the fc/cya percentage, the slower the reaction.

    In any case, one should be careful about relying on the pH test with fc over 10.

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    Patrick_B's Avatar
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    Re: pH is purple!

    Quote Originally Posted by easttn View Post
    I guess its going to be like a Bigfoot sighting. "I know what I saw" but everyone else will think your crazy. I knew I shouldnt have said anything about it. I guess I will continue doing the impossible.
    No, that's the whole idea. You shouldn't be trying to get pH with phenol red and high FC.
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