I wanted to share my experience with the TF100 test kit that I just purchased.
I did all the testing according to the directions on the laminated sheet included in the kit. My results were similar to a recent local Leslie's testing except for two.
My TA 190 and CH 300
Leslie's TA 90 and CH 240
I got to think how could it be so different?
I got this kit as it seemed like a general consensus in this forum that Leslie's testing cannot be fully trusted. I could imagine this to be true as Leslie's modus operandi is to make money by selling pool chemicals. But I would think they cannot willfully or unknowingly be testing that is way off. The plausible explanations of my test numbers being different from Leslie's were;
1. the TF test kit is no good.
2. Leslie's testing is no good.
3. I am not doing the test properly
I repeated the TA testing two more times and got 210 and 190(average of 200). As the three numbers were very similar, I had ruled out number 3. I was not so concerned about CH at this time as it was within normal range.
I brought a water sample to the same Leslie's for repeat testing which showed TA 100 and CH 220. I noticed that Leslie's uses a electric stirrer while doing TA testing. hmmm, i thought. While talking to one of the workers, I was told that the testing droppers should be held 90 degree vertically as opposed to holding it obliquely (as I was doing) to obtain more consistent drop volume. hmmm.
I got back home and re-did the TA testing (three times) while vigorously agitating the testing tube with each drop of the reagents off the bottles in a vertical fashion. I could not believe the difference it made. More I agitated the test tube, the lower the TA reading. The numbers were 170, 150 and 110. The last one with almost constant agitation to emulate the electric stirrer. I even wet-wiped the tip of the reagent as per the direction this time (something about static).
It turns out that my 110 is not "too much off" from 90 - 100 that Leslie's was getting (I am assuming that the lowest number is the most accurate).
I would think that CH testing may also be affected quite a bit by the agitation of the test tube. I will repeat it soon.
I think it is important for people to know that to get an accurate TA reading, the technique is important as wrong test numbers may lead to unnecessary acids being poured into the pools. High TA seems to be a common issue in this forum.