Iíve been using TFP methods and TF-100 test kit for 3 months now and still have difficulty with the CYA and CH testing. I test these weekly because we have new plaster, and thereís so much helpful information on this site, so youíd think Iíd have it figured out by now, but I want to be sure Iím doing this right. I finally ordered the CYA Standard and CH Standard solutions, thinking it would help me interpret the test results, but I still have problems with both tests and hope I can get some guidance.
(1) When I tested the CYA Standard, which should read 50 ppm, I read it as 40; even at 30 the black dot was sorta visible but arguable (hubby and I disagreed at 30). We repeated the test a few times and tried looking at it in different sunny spots, inside the pool screen and out in the yard, but with the same result. The pool water test, done in the same time frame, was about the same Ė arguable at 30, fuzzy but visible at 40, a close match to the standard, which means 50. So, should I adjust my interpretation and assume my pool CYA is 50, and calculate my chlorine needs based on 50? Iím ok with that but not sure what Iíll do when the CYA varies from this reading Ė Iíll be guessing. Iím fairly sure we followed the instructions correctly, and have tried tips and tricks I found here Ė any suggestions?
(2) If I misinterpret my CYA and over-dose on the FC, will it hurt anything, besides being wasteful?
(3) I worried that an erroneous CYA measurement would affect the CSI calculation (I check this with my daily testing). But playing around with Pool Math, it looks like a CYA difference between 30 and 50 doesnít affect the CSI calculation terribly, is that correct?
(4) The CH Standard testing was delightful, a very crisp and clear change from definite pink to definite blue, exactly at 200 ppm. My pool sample, however, looked anemic by comparison, very pale pink and VERY pale blue (nearly colorless), an almost imperceptible change with no change in color intensity even after adding several more drops of reagent. I do use a Speed Stir. Iíve been interpreting my CH as 200 ppm, but is it actually lower? (200 is our target, which is lower than TFP recommendations, but the Wet Edge warranty specifies a CH ďnot to exceed 200 ppm.Ē) With new plaster, I want to be sure my CH testing is accurate, and Iím not so sure. Any suggestions?
Thanks in advance for the help! Sorry for the long post - please let me know if this should have been 2 separate ones.