I am new to this and have only done about 10 CYA tests in my life starting about 2 weeks ago. However I am getting some huge swings in the level, I started out low, added CYA as per poolmath shot up to 40. I was happy and was going to use trichlor and when it got to 60 (I was hoping end of season) I would do a water exchange to lower for next season, a week later I am reading 50, so figured better stop trichlor that is bringing up way to fast, week has gone by I test yesterday I am reading 20. Any Ideas on what I am doing wrong? By the way the pool has not been used very much and I usually test CH & CC 2 x/day early AM & 6-7 in PM. overnight loss usually < .5 on FC, daytime loss about 2, this has really not fluctuated over the past week and a half since I came off slam, slam was only a few days because with knowledge from here and using pool store # till I got the test kit. I was dialed in close and my pool store testing was pretty accurate except for CYA could not read, they said it was because TA too low but TA was 70 so while it can be raised a little I did not think it a major problem.