Weeks ago, I had to shock my pool and then ran my SWG at a pretty high level. I had to finally cut that out to get my FC levels to settle down, and they took DAYS to do so. I had the SWG set to like 15% and still my FC was falling very slowly.
Once I got near my target level, I moved my SWG to 25 then eventually up to 35% to keep those levels. It seems as though there is a buffering effect going on in the pool such that my FC levels were very high for a while till I burned off the excess (bound up in another form along with the CYA), and so it takes my SWG running higher to keep the steady state levels where I want them or to rebuild the buffer.
Can someone who really understands how CYA works to "protect" the chlorine and whether it acts as a buffer shed some light on this situation?