On another thread I mentioned that I had out of curiosity compared my results using the TF-100 kit and those of a local pool store (Leslies). We pretty much agreed on all but the CYA test.
Immediately after draining and refilling:
Pool store: 30 ppm
TF-100: <20 ppm
After using trichlor tablets to raise CYA:
Pool store: 45 ppm
TF-100: 30 ppm (or thereabout)
Both are acceptable numbers, of course. After realizing from other threads on this site that the test is based on equal ammounts of pool water and test reagent I questioned whether or not I was properly filling the included test bottle. I then repeated the test using one of the other measuring cylinders in the test kit and measured out 14.6 cc (I think that is what is indicated on the mark I used) of each pool water and reagent. The results as observed by my wife and me were now 45 ppm. It appears as if the previous tests were due to "operator error".
Actually, based on an "after drain" reading and the calculated (per pool calculator) ppm value I should have achieved using the number of trichlor tablets used, the final ppm value should be somewhere in the mid 40's.
Anyway I now have a bit more confidense in measuring each component rather than using the pre-marked bottle. Has anyone else had this experience?
By the way, I am by no means attempting to insult or blame the test kit. It's the best one on the market. This "operator" just needed some adjustment.