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Thread: No test kit gives a consistent result

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    No test kit gives a consistent result

    i just spent 3 hours reading everything posted in this forum regarding testing water. the only conclusion i have come to is no one here has come to a conclusion. i maintain over 300 pools on long island and have the answer for everybody. i have used every single testing gimmick and professional kit on the market, and the only consistent result is no test kit gives a consistent result. you can test the water 5 times at the same time and all the readings will be different. the best advice is if you are here in this forum for a little advice about what to use on your new pool, is get yourself an inexpensive 7 dip test strip, and stay out of the pool store as much as possible. testing your pool water is like taking your temperature. it will be different every single time, no matter how accurate the thermometer and adding chemicals to the pool when your readings are only slightly off is like taking medicine when your temperature is 98.5 or 98.7. stick with the 7 dip strip and only go to the pool store to verify your results if you are having a problem with the pool. the chemical advice on the other parts of this forum are excellent, with nearly perfect information on the use and application of chemicals. i would advise all new pool owners to remember that anything you put in your pool water will always be there, only pure water will evaporate so be careful what your buying and adding because years later it may still be there.

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    JasonLion's Avatar
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    Re: No test kit gives a consistent result

    Welcome to TFP!

    While I agree that test results will tend to be different every single time with any test kit, it is important to look at the range of variation in test results between different test kits and different people using those test kits. The Taylor chemistry will give much more tightly grouped results than test strips will. The Taylor titration tests will be +-one drop better than 95% of the time, while test strips tend to have five to ten times that range of variation. Test strips also have a significant percentage of wildly wrong results, while the Taylor chemistry is nearly always within 30% (and usually much better than that).

    Novices using test strips will eventually run into a wildly wrong result and will typically trust that bad result enough to add some chemicals that they really shouldn't have added. The frequency of similar problems with the Taylor chemistry is far far lower.
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  3. Back To Top    #3
    Guest

    Re: No test kit gives a consistent result

    Welcome to the forum.

    I have been testing water for a very long time and I have to disagree with you. A good drop based test kit can give consistent results IF the testing procedure is properly done, which it usually is NOT. I worked with 3 CPS's this summer at a large commercial installation (2 pools, 2 spas, kids splash zone) and they were clueless about testing. Most of the members on here could probably do a better job. Two of them didn't even know how to read a Taylor 2000 series comparator for the DPD test and didn't know there was both a chlorine ANd bromine scale on it! They would read the 3 ppm as 3.6 because the bromine scale is 6 when the chlorine scale is 3! I quickly straightened that out when I discovered it. This experience let me see first hand that many "professional' people don't take the time to test properly (IF you have 300 pools to test spending the 15 minutes it REALLY takes to do a calcium hardness titration PROPERLY is just too much time. I also work in a pool store and I do a LOT of water testing. In a retail store time is money which is why store testing is often not that good. They want to get it done fast and if the testing shows that you need to add chems so much the better, it's a possible sale!

    I happen to have a chemistry background with experience in analytical chemistry (and had participated in a research project at the University of Miami School of Marine and Atmospheric Science on oceanographic physical chemistry in the 1970's so part of my experiece is also in laboratory procedurs and proper techniques) so I do know something about what I say.

    Test strips are NOT a good choice for one very simple reason, they just don't have the resolution of a drop based kit. For example, most (all?) strips have a resolution of 40 ppm for a TA test (and really are not that accurate on this test anyway (there is a difference between accuracy (Are the results repeatable within a certain range?) and precision (How small or large an increment can be measured?). Now, in reality TA should be kept in a smaller range than 40 ppm, particularly if you are having problems with rising pH so they are just NOT up to the job. pH tests on strips are just about useless. I have only come across one strips that actually has a color block for pH between 7.2 and 7.8 and that is the Taylor. I have used several different brands and styles of strips (Hach/AquaChek 4 way and Select 7 Way, LaMotte 6 way, AquaChem (Chemtura) 6 way, HTH 6 way --rebranded Taylor strip) on the same sample to compare results and got widely different results. CYA tests ranged from 0 ppm to 150 ppm (acutal CYA 70 ppm as per Taylor and LaMotte colorimeter) for example. BTW, when CYA testing was repeated with a Pentair liquid reagent test it also gave 70 ppm!

    Also, test strips cannot test calcium hardness but only total hardness which is useless for determining the calcium saturation index. The only use for a total hardness test is if you are using the Hamilton Index from United Chemical and running a high pH pool (and there is no research to support that this actually works other than the word of United chemical and the research done by the late Jock Hamilton. Interestingly enough, most of United's bromine based products work better at higher pH so could there be a reason why they came out with a system to run high pH pools? You tell me.)

    Even a cheap drop based testkit from Walmart will give more consistent (acuurate) results than a strip. The only strips that I have come across that have value are the AquaChek salt (actually a reverse titration test) and the LaMotte borate (only one that as color blocks that are readable above 30 ppm!)

    A GOOD drop based kit such as ones from Taylor or LaMotte, in the hands of someone doing the test carefully and not rushing through it like most pool stores or maintenance people (or CPOs!) can and will produce consistent and precise results. It's not hard but it involves learning the proper procedures. Most, if not all, pool owners who decide to take control of their water do learn how to test properly and I would take their test numbers above that of the tests on the same water done at a pool store or even by a CPO!

    (Getting off soapbox now! )

    BTW, if you have NOT used an FAS-DPD test for chlorine then you should really try it. It is vastly different than a DPD test and can test FC levels up to 50 ppm with a precision of .2 ppm! The endpoint of the titration is distinte (red to colorless) with no ambiguity and even someone who is colorblind or who cannot differentiate between shades of red (about 1 in 5 males) have no problem with this test!)

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    Re: No test kit gives a consistent result

    So, waterbear, what is the proper way to test CH with the Taylor reagents? I know I haven't spent 15 minutes doing it.
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    Re: No test kit gives a consistent result

    The endpoint of the titration is distinte (red to colorless) with no ambiguity and even someone who is colorblind or who cannot differentiate between shades of red (about 1 in 5 males) have no problem with this test!)
    Guilty....
    Now I know I am one of those 5 even though I am sure I am not color blind, no wonder I can't really tell the difference of red colour chart of PH 7.6 or above...it sure looks the same to me. Thank you Obi-Wan.

    So in theory if a pool guy with poor red color perception like me maintains PH7.6 and do not do the acid demand drops, that could result in consistent high PH without knowing ?

    ADD ON : Yes, I want to know too that 15 minutes for CH test. Thanks for reminding Malcolm
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    Re: No test kit gives a consistent result

    Quote Originally Posted by Malcolm
    So, waterbear, what is the proper way to test CH with the Taylor reagents? I know I haven't spent 15 minutes doing it.
    Add the first reagent and swirl for about 20-30 seconds to mix (to precipitate out any magnesium so you are only testing calcium hardness and NOT total hardness!). Add the indicator and swirl until mixed well. then swirl for 20-30 seconds between EACH DROP of titrant added. If you want to speed up the test a magnetic stirrer is a big help since it mixes the reagents and the sample very quickly and the drops can be added almost as fast as they can be dispensed. I would give about 3-5 seconds between drops in this case.
    portable-magnetic-stirrer-from-apollo-pools-t1489.html
    The swirling between drops is what most people do not do, it's time consuming but it really is necessary for the titrant to mix and react with the calcium in the water. Otherwise you can get an inaccurate endpoint and sometimes you will get purple 'floaties' that mask the blue endpoint color so you overshoot the calcium reading.

    Also, if you suspect metals in the water, get a purple 'floating endpoint', or purple 'floaties' that settle when the sample sits for a few minutes to reveal the blue endpoint then there is an alternate testing procedure.
    Assuming a high resolution test (25 ml sample and each drop of titrant = 10 ppm CH) add 6 drops of the titrant FIRST and swirl for about 30 seconds, add the 20 drops of reagent #1 and swirl for 20-30 seconds, add the indicator and swirl to mix well, then start the titration but start counting the first drop as drop 7 (and remember to swirl for at least 20 seconds bewtween drops. You want the water in the test vial to be constantly moving in a circular motion by swirling the vial as you add the titrant while you are timing. If you hold the vial still that DOES NOT count at the 20-30 seconds since you are not mixing. Like I said a magnetic stirrer is a great asset for this test (and also the FAS-DPD, TA, and chloride (salt) titration tests.

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    Re: No test kit gives a consistent result

    Quote Originally Posted by SPP

    Guilty....
    Now I know I am one of those 5 even though I am sure I am not color blind, no wonder I can't really tell the difference of red colour chart of PH 7.6 or above...it sure looks the same to me. Thank you Obi-Wan.

    So in theory if a pool guy with poor red color perception like me maintains PH7.6 and do not do the acid demand drops, that could result in consistent high PH without knowing ?
    Which test kit? The Pentair color blocks are hard to read. LaMotte and Taylor are much easier but the colors above 7.6 are close with phenol red. Basically you want a red color with NO bluish or purple cast (pink color in some cheaper test kits such as the pentair). It can have a slightly orange cast. This would be a pH of around 7.4-7.5
    If you use your acid and base demand reagents to run through the colors that the indicator produces you will soon learn to differentiate the colors. While you are learning have your wife, girlfriend, sister, or other female you know read the test. Women have much better color perception than men but men CAN learn it it not colorblind.

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    Re: No test kit gives a consistent result

    Aha...I buy Pentair 5 bottles test kit, 78HR...even though I have TF-100.... and keep buying it because it has that #3 solution to do acid demand test. Not that I want to know the acid demand, I need it to bring down the color to at least 7.2 or 6.8 where my eyes definitely know its different than 7.6 and 7.8. I do notice the 8.2 is redder though.

    I did not bother with the Taylor K-1000 that came with the TF-100 since I thought at a glance it's the same but I can't do acid deman test on a Taylor... oh wait...wait...TF-100 has TA reagents called R-0009, dang...that is the same as #3 acid demand on Pentair isn't it ? I can use that R-0009 as acid demand on the Taylor PH right ? I am so afraid different brand uses different "formula" that I dare not test unless there is a written instruction.

    Now that you mentioned the Taylor color bar is better, I just realized indeed it is better. I just opened it up and take a closer look. Taylor 7.5 to 7.8 does look different for my eyes, unlike Pentair 7.6 and 7.8...YIPEE !!!!!!!!!!!!! Thank you, you saved me a K-1000.

    So I am not that color blind after all...I been brand blind...

    I will do some test in good daylight ( I will do it in the shade ).

    Thanks again WB...indeed you are a King Size fountain of information. If youa are a flash memory card, its Terra Byte class...not Giga Byte.....

    PS As far as I know, Terra Byte flash memory card is not available yet...not in CF size.
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    Re: No test kit gives a consistent result

    Quote Originally Posted by SPP

    I can use that R-0009 as acid demand on the Taylor PH right ?
    No, Taylor makes different acid and base demand reagents. They ARE available for the K-1000 comparator from Taylor, btw.
    I am so afraid different brand uses different "formula" that I dare not test unless there is a written instruction.
    You are correct. Using the TA titrator from the Taylor kit will NOT work!

    Now that you mentioned the Taylor color bar is better, I just realized indeed it is better. I just opened it up and take a closer look. Taylor 7.5 to 7.8 does look different for my eyes, unlike Pentair 7.6 and 7.8...YIPEE !!!!!!!!!!!!! Thank you, you saved me a K-1000.

    So I am not that color blind after all...I been brand blind...

    I will do some test in good daylight ( I will do it in the shade ).

    Thanks again WB...indeed you are a King Size fountain of information. If youa are a flash memory card, its Terra Byte class...not Giga Byte.....

    PS As far as I know, Terra Byte flash memory card is not available yet...not in CF size.
    LOL, Glad to be of help! I think you will find the Taylor comparator much easier to use! I hold it up against blue sky to read it but NOT in direct sunlight. Works best for me.

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    Re: No test kit gives a consistent result

    OK.... Thank You Obi-Wan......

    I will post for members here, the photo of PH shade of red for Pentair 78HR, Taylor K-1000 and some funny brand EMAUX
    So now I think the logic is quite clear to why testing can be inaccurate or different people will read different, I mean for PH
    The photo is taken with no flash under a white fluorescent light, but I do not know the color temperature of my light.

    01. You could be like me...not very sensitive towards red color.

    02. Your test kit color bar confuse you because different brand has different color quality print on the color bar....like it did to me

    03. You maybe testing indoor or insufficient light and do not use a white background, so different results maybe "seen"

    04. You maybe testing at night where some out door lights are those soft "colored" bulbs that looks yellowish like halogen kind of light

    That's all I can think of.
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    Re: No test kit gives a consistent result

    Those pictures really illustrate the difference between a GOOD testkit and a cheap one!

  12. Back To Top    #12

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    Re: No test kit gives a consistent result

    Dang...I live on the wrong side of the globe as far as good test kit is concerned.

    If I am in the US, I will buy many-many test kit for the fun of testing, they are so cheap there !!!

    True in many sense, money does talk and we are talking of a bit of extra money only...and for a pool costing a few ten thousands of dollars.
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    janeann11's Avatar
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    Re: No test kit gives a consistent result

    waterbear,

    Thanks so much for the CH testing instructions. I've had a really hard time nailing down my reading. The Taylor instructions are very cursory and only say to add drops and swirl until the sample turns blue. I will try your steps tomorrow.

    Thanks, Jane

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    Re: No test kit gives a consistent result

    No comments on the TF-100? 8)
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    Re: No test kit gives a consistent result

    Well, I like the TF-100 test kit so much....the FC and CC test for chlorine is just fantastic.

    Later you will surely need to buy the FAS/DPS chlorine test kit when you run out of it, here is the truth I found out :
    possible-formula-to-estimate-reagent-usage-t9312.html
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