PH Difference between K2006 & K1000

[Cookieman]

When I got a low ph reading from K2006 (7.0) I double checked it with the k1000 because my ph remains fairly stable at around 7.5. The K1000 returned a reading of 7.4/7.5. What could cause this difference between test kits and which one I should react to?

[Watermom]

What was the chlorine level when you tested the pH?

[Cookieman]

The ph did get high about 2.5 weeks ago when I went back to chlorinator - the adjustable valve evidently wasn't working right and we were on vacation a few days. It got up to around 15. My range is 3-6 on best guess chart based on my CYA. Since then, I have kept it in the 3.5 - 7.0 range. Through all this, the ph difference between the two kits have remained the same. There is a definite color difference depending on the kit. Hopes this answers your question.

[chem geek]

Sometimes the comparator colors in the K-1000 aren't as accurate so first off compare the comparator tubes of the K-1000 vs. the K-2006 to see if they match or are consistent. If not, then that's the main source of the problem. You can also do parallel pH measurements with samples in each tube and compare the color of the samples side-by-side. Remember that you aren't trying to match saturation, but rather hue. This can sometimes be tricky to do. You may find that you can use fewer pH Indicator drops in the K-2006 for a less intense color that is easier to match against the reference colors. The phenol red indicator is the same in both kits except for concentration and that should only affect saturation and not hue.

7.0 will be quite yellow while 7.5 will be more of an orange-red so they should be quite dramatically different. With CYA in the water, even a high FC doesn't affect the pH test until after a minute or so (i.e. that reaction is apparently slow). If you still find a significant difference in hue (after trying more or fewer drops of indicator to try and get the saturation level to be similar), then there may be something wrong with one of the indicator dyes. These are organic dyes and they do degrade over time which is why Taylor recommends replacing them once a year though in practice one can usually go 2 years before replacement. Taylor says (http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=2) that for the phenol red indicator dye "As it degrades, the solution changes from its original red color to a yellow or purple."

[Cookieman]

Color charts on the tubes match up pretty well. Started doing parallel tests, and only once did they come close to matching. The sampling with the k1000 consistently produces a more reddish orange color than the k2006 in my sampling over the last few weeks. Dye looks good - still red and kit is less than 8 months old. While I understand I need to be matching hue, not sure I understand using fewer drops, as I have not had a problem in matching sample color with comparator tube. I did attempt a couple of times adding more drops and it did intensify the hue, but only moved the the "visible match" up one on the scale. To me it made it a bit harder to match the sample to the tube colors. I have not reacted to the low ph yet, but ready to do so if it gets worse. Thanks

[BigDave]

...The phenol red indicator is the same in both kits except for concentration...My apologies for asking, but, are they the same? The K-1000 comes with R-0014, and the small comparator that reads 6.8-8.2(6.8, 7.2, 7.5, 7.8, 8.2). The K-2006 comes with R-0004, and the large comparator that reads 7.0-8.0(7.0, 7.2, 7.4, 7.6, 7.8, 8.0). I thought (don't know why) that the R-0004 was stabilized for higher chlorine.

[Cookieman]

Yes the scales on the comparator tubes have different numbers/ranges. The hue/colors on the tube appear comparable to me. The 7.2's for both tubes look the same. The 7.6 on the large is slightly redder than the 7.5 on the smaller tube. The R numbers are different, but I just thought that was due to the smaller sample size of the K1000 so the saturation/concentration would be different. If the R0004 is made for higher levels of chlorine, I would like to confirm that. I always thought the smaller kit was to serve as quick chlorine/ph check to save on the chemicals in the larger 2006 kit. Thanks

[chem geek]

I wrote to Taylor Technologies about this and they want the lot numbers on the two reagents (it should be printed on the bottle) so could you please post what those are for the R-0004 and R-0014 so I can let them know and they can investigate further?

[waterbear]

My guess is bad reagent if the K-1000 is always reading about 7.5 (orange-red). I have seen this happen before. How old is the reagent for each kit? The other possiblility is contaminatin (pissilbly from the TA) in the large comparator tub in the KJ-2006. Make sure that the tube is clean and rinsed out with your sample water a few times before you test.)
They should be testing exactly the same ( I use both all the time). If they are not it is most likely bad reagent or a contaminated or dirty comparator. Easiest way to check it to get new reagetns for both, they are not expensive.

[Cookieman]

Lot# for K1000 0014 is 2123C; Lot# for K2006 0004 is 3024B. I always rinse the tubes before filling with sample water or going to a different test, but maybe I need to do a better job....will try that. Both kits are less than a year old, but will be a year in Nov/Dec this year. Will order more of both. Thanks for the help.

[giroup01]

Reagents are fresh (approx 6 months to 1 year from manufacture date)

[chem geek]

I heard back from Taylor Technologies who wrote the following:



I reviewed your concerns with the Production Manager and the Quality Control department, they both confirmed that the lot numbers you provided where made to our quality control specifications. I ran several pH tests using both the K-2006 and the K-1000 color comparators. I tested standard pH solutions 7.0,7.2,7.6,7.8 in both comparators using a fresh lot of R-0014 in the K-1000 comparator and a fresh lot of R-0004 in the K-2006 comparator.

I found that each standard measured exactly to the K-2006 color comparator. K-2006 ranges are ( 7.0,7.2,7.6,7.8). The K-1000 color comparator has different ranges ( 6.8,7.2,7.5,7.8,8.2). With the K-1000, I found the 7.0 standard solution measured between the 6.8 and 7.2. The 7.2 solution measured exactly at 7.2 .
The 7.6 standard solution measured between 7.5 and 7.8 on the comparator. The 7.8 standard solution measured exactly at the 7.8 on the color comparator. I viewed all tests under the same light source.

Since the ranges are different between the two color comparators there was some estimating with the K-1000 when testing the standard solutions. Keep in mind this test is a color comparison and it can be subjective when reading your results compared to another person running the same test.

As [name deleted] mentioned in the previous email, the difference in the reagents are minimized as long as they are used correctly (with the correct sample size, number of drops and the same light source).

Note that they did not test using pool water, but standard solutions. I don't know if that makes a difference (maybe chlorinated water affects bad reagents more?). If you want to pursue this, I suggest you contact Taylor directly and maybe you can get fresh reagents and send back the ones you have so they can reproduce the problem. You might also try measuring the same sample of dechlorinated water with the two kits.

I'll have Ben PM you with the technical support contact person info.