LaMotte ColorQ Water Tester

I got an RMA number and I am now returning mine. I am VERY skeptical about the accuracy of this meter. All of the results were off for me by quite a bit. Nice idea, poor execution.

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Originally Posted by Amir

Ront,
My cya reading with colorQ has not gone above 9 where my cya should be about 50. According to laMotte CYA is temperature dependent so you can not just add a number to what you get from the colorQ to be accurate since the water temperature varies with the season . In order to get this machine to work right they should take into account other factors in addition to color and the machine needs to be more sophisticated and probably more expensive. I for one would have paid another $50 for a more reliable machine. I guess if you think of the machine as a test fro cl, alk, ph and ch only it is not bad.
Regards

Amir

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It is very easy to change the Temp of a 5 ml sample. In order to maintain consistency, I have reduced the temp of the sample to 75, very simple by dipping tube into cooler water for a couple seconds. Anyway, 6 sucessive tests have been between 29-31 for the CYA. So, while it may be showing low, at least it is showing low consistently. This is not a big deal, since the CYA test does not need to performed on a regular basis as does CL & pH.

I wonder why Taylor CYA test that uses liquid melamine reagent is not so temp sensitive. That test also depend on the water to get "cloudy" but has good results consistently.
Amir

Ront,
If you get 29 with the correct water temp and the CYA should be 60 and 70, there is something wrong with that machine. They should not advertise CYA accuracy if you do everything right and the results are off by that much.
Amir

Quote:

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Originally Posted by Amir

Ront,
If you get 29 with the correct water temp and the CYA should be 60 and 70, there is something wrong with that machine. They should not advertise CYA accuracy if you do everything right and the results are off by that much.
Amir

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Please reread my post near the beginning of this thread where I posted what tech support at LaMotte said about the meter. CYA is +/- 20 ppm so your reading of 29 is within spec. It can be as high as 49 and you stated that your CYA should be around 50 ppm. When doing any kind of water testing you have to look at the precision of the test. The meter is probably more accurate than a 'disappearing dot' test any day within the limits of it's accuracy since it removes the subjective element of 'when has the dot actually disappeared?" You can have 3 people do a disappearing dot test on the same sample and they can get readings that are not even close to each other! Common testing methods for CYA as used in home test kits (and even some very expensive professional ones) are a rough guide at best and should be used as such. It's really not appropirate to say "my cya is 70 ppm" since it can be off by as much as 30 ppm with conventional testing methods. At best you really only have a ballpark figure of where it is with the types of tests included in most water test kits.
As far as the calcium hardness problem, that seems to be a limitation in LaMotte's chemistry that is used with colorimeters. We use a Waterlink Express at work that uses vials of dry reagents. The upper limit of the CH test is supposed to be about 500 ppm but if the hardness is higher than that the test will still only report about 450-500 ppm. I have spoken to LaMotte tech support on this and they suggested to titrate when I got high calcium readings with the Waterlink. Interestingly, LaMotte does offer kits that include calcium hardness titration tests also. Using a meter certainly speeds up testing but does not necessisarily REPLACE other forms of testing. You need to know the limits of the equipment and use the apporpriate test under the appropriate conditions. Don't throw the baby out with the bathwater!

Just my 2 cents! (And no, I don't have a ColorQ. I use Taylor chemistries to test my own pool! I still think the ColorQ is a viable tool in water testing when used properly.)

One final note about CYA testing. Temperature does affect the test to some degree whether you use liquid or dry reagents as does how long you let the sample stand before testing. That is why I have said in several previous posts about the Taylor test to make sure the sample is between 70-80 degrees and to let the sample stand for about 5 minutes after shaking it for 30 seconds and to shake it again to disperse the precipitate before dispensing it into the view tube. I suspect that if you let the CYA sample sit for about 3 minutes before reading it in the ColorQ you will find that your CYA readings are more in line with the Taylor one.

Waterbear,
thanks for the comment. My CYA should be around 50. I have never been able to get a reading form colorQ more than 9! Retesting the same sample gave me different measurements and surprisingly the water seems to get less cloudy the longer it sits! Maybe it gets warmer. This was not apparent with the liquid reagent and the dot. Temp here is over 90 in daytime! I have followed the instruction to the letter using a stopwatch - I am surprised that lamotte does not ask to shake the sample but just turn it upside down three time and once before placing it back in the tester. the pool was plastered and filled in June. The only thing in the pool has been trichlor tabs, bleach, CYA(6 lbs), Muriatic acid and baking soda. temp 80, PH 6.6, TA 87, CH200, CL 3.8, CYA ~50. I hope there is something wrong with the meter since I really like it. I might even keep it just for the other tests.
Regards

Amir

inverting the vial 3 times is the correct procedure but you have to make sure the tablet is fully dissolved. Also high water temp will give a lower reading since the precipitate will be more soluable so having the sample at the correct temperature is important. We get many customers who leave a water sample in their car all day! (I TRY to tell them that this will affect the test results but some of them just don't care.) The first thing I always do is to take the temp of the sample and if it's above 80 degrees I stick it in our freezer at work for a few minutes to bring it down before I test it.

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Originally Posted by waterbear

inverting the vial 3 times is the correct procedure but you have to make sure the tablet is fully dissolved. Also high water temp will give a lower reading since the precipitate will be more soluable so having the sample at the correct temperature is important. We get many customers who leave a water sample in their car all day! (I TRY to tell them that this will affect the test results but some of them just don't care.) The first thing I always do is to take the temp of the sample and if it's above 80 degrees I stick it in our freezer at work for a few minutes to bring it down before I test it.

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I second Waterbear's comments and add that based on my 2 months experience with the colorQ, you need to let the CYA sample sit for at least 5 minutes before reading or it will read low and get that sample below 78F. Also, if analyzing samples with chlorine higher than 4ppm, you need to let all of the samples with reagent added sit for a minimum of 2 minutes before reading with the meter or you may get erroneous readings on FC, TC, and pH reading. My CH always reads low as compared to Taylor, but it's still inside the +/- 40ppm window

Quote:

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Originally Posted by waterbear

Please reread my post near the beginning of this thread where I posted what tech support at LaMotte said about the meter. CYA is +/- 20 ppm so your reading of 29 is within spec. It can be as high as 49 and you stated that your CYA should be around 50 ppm. When doing any kind of water testing you have to look at the precision of the test. The meter is probably more accurate than a 'disappearing dot' test any day within the limits of it's accuracy since it removes the subjective element of 'when has the dot actually disappeared?" You can have 3 people do a disappearing dot test on the same sample and they can get readings that are not even close to each other! Common testing methods for CYA as used in home test kits (and even some very expensive professional ones) are a rough guide at best and should be used as such. It's really not appropirate to say "my cya is 70 ppm" since it can be off by as much as 30 ppm with conventional testing methods. At best you really only have a ballpark figure of where it is with the types of tests included in most water test kits.
As far as the calcium hardness problem, that seems to be a limitation in LaMotte's chemistry that is used with colorimeters. We use a Waterlink Express at work that uses vials of dry reagents. The upper limit of the CH test is supposed to be about 500 ppm but if the hardness is higher than that the test will still only report about 450-500 ppm. I have spoken to LaMotte tech support on this and they suggested to titrate when I got high calcium readings with the Waterlink. Interestingly, LaMotte does offer kits that include calcium hardness titration tests also. Using a meter certainly speeds up testing but does not necessisarily REPLACE other forms of testing. You need to know the limits of the equipment and use the apporpriate test under the appropriate conditions. Don't throw the baby out with the bathwater!

Just my 2 cents! (And no, I don't have a ColorQ. I use Taylor chemistries to test my own pool! I still think the ColorQ is a viable tool in water testing when used properly.)

One final note about CYA testing. Temperature does affect the test to some degree whether you use liquid or dry reagents as does how long you let the sample stand before testing. That is why I have said in several previous posts about the Taylor test to make sure the sample is between 70-80 degrees and to let the sample stand for about 5 minutes after shaking it for 30 seconds and to shake it again to disperse the precipitate before dispensing it into the view tube. I suspect that if you let the CYA sample sit for about 3 minutes before reading it in the ColorQ you will find that your CYA readings are more in line with the Taylor one.

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Yes, I understand the +/- 20ppm factor. So, during my testing, as long as I am getting consistently the same results, I can live with that. and now 6 or seven sucessive tests have been between 29-31 ppm. If I was getting wildly ranging results, that is a different story.

Donald,
don't you think LaMotte should or would have indicated in their instructions the longer length of time for samples. I can understand that they want to make it as simple as possible, but at least a footnote? last night I put a sample of the water with a thermometer in the refrigerator until the water was at 75F and tested for CYA according to their test procedure. The results was a CYA of 12. ups picked up the unit along with a sample of my water. I hope that this problem is just specific to my colorq and other unit or the replacement one will be more accurate.
Regards

Amir