I have a 23K gallon inground pool that has had high cyanuric acid levels this year already. The problem is a carryover from last year, which I thought I had fixed by draining half of the water last fall. However, I was told by my local pool store that draining from the shallow end did not provide the full benefit because CYA is heavy and is more concentrated in the deep end of the pool (Has anyone head that?).
Anyway, after not being able to get my chlorine readings to stick, I had the CYA checked and found it to be at 150 ppm. I drained 1/3 of the pool water from the deep end and now have the CYA down to 70 ppm. However, it is still taking more chlorine than normal to maintain a reading. Traditionally I have used di-chlor granular but switched to tri-chlor tabs this year because of the lower CYA content. My pool guy has suggested using a flocculent agent before draining more water because he says that the flocculent will capture some CYA within the solids formed. Does this make sense?