CYA Testing. Oh Brother!

[Watermom]

The K-2006 does use the vanishing black dot test.

(Hi, BTDG ....... uhhh, I mean, son!)

[waterbear]

The difference is most likely because of the lighting that was used to read the test since it is read from the top of the tub AND because the second store did not clean the tub out after each test (just bad practice and all the more reason to get your own kit). Get yourself a K-2006 and test the CYA yourself and clean the tube after and you will be fine!

FWIW, pool store salt tests are about as accurate as pool store CYA tests, which means they are not. If they are using a meter they most likely are NOT calibrating it often enough ( because the standard calibration solutions are not cheap). If they are doing a titration they are very possibly overtitrating, which is very easy to do with the standard chroamte/silver nitrate titration for chloride (such as the Taylor salt test kit). If they are using strips they are most likely not letting them sit long enough (since strips need about 10 minutes according to info on the AuqaChek/ETS/Hach website that is not on the bottle of strips and most stores are not going to take that long to test your water, particularly if they are busy!)

Best bet, test the water yourself!