Hello All.. I am new and this is a first post for me. I have new plaster and am really trying to get the water right. I have taken water to the local pool store three times since filling last week. First trip the CY was 0.. great. New plaster seems correct. In a 17,000 gallon pool I added 2.25 lbs of Cyanuric acid. Back to the pool store 3 days later and the CY reading was 15. Seems about right? I didn't add any more Cyanuric acid and 3 days later they say the CY is 40. I tested it at home with the Taylor kit and when the small viewer was completely full.. which indicates less than 30 ppm.. the black dot is plain as day. The solution is even a little cloudy. Probably closer to the 15. This test is not had to do. I am using liquid chlorine and am losing chlorine on this sunny day. It seems that the 15 makes more sense than 40. I guess I need to try another pool store or believe the Taylor kit? Your thoughts and advice is appreciated.