I work in a pool store (mostly testing water) and I can tell you that the test results you get are only as good as the person doing the test. I just took some water from my pool yesterday to be tested at a local competing pool store that is closer to my house than the one I work at (I had run out of CYA reagent and they carry it. The one I work at doesn't) and the young girl doing the tests was very sloppy. When she tested for FC I asked to see the comparator (I already knew what it was since I had just done it at home with the exact same Taylor comparator and reagents and it was also the same as my TC with an OTO test) and she read it 2 ppm lower than I did. Either my eyes are off or hers are! She also did the CH test until it just turned purple and got a lower reading than I did at home. This is ONE test that I really know how to do properly becuase I have been keeping saltwater reef aquariums for about 30 years now and that is a standard test for them! I KNOW I have more experience with that test then she does even if she had been doing it every day for the past few years! Watermom is right on the money when she said that the endpoint is a distinct blue.

The CYA test is a bit tricky until you get the knack. What I do is hold the tube at waist level in the shade as I add the mixture of reagent and water until the dot disappears. The tube with the sliding dot should give the same results if the test is done properly. Once again it is the procedure of the person doing the test that matters.

Bottom line is this....test your water yourself and believe your results. If you are not sure how to do a test you can get a lot of pointers here on the forum!