My chlorine was 9.5 ppm this morning when the pH was well over 8. Yesterday morning my chlorine was 9.5 ppm and my pH was 7.6. I added nothing but maybe 1/4 gallon of chlorine last night. The same thing a few weeks ago....just a big spike in pH. It wasn't even a slow rise, just a big spike from one day to the next. I also tested a few times and from different areas of the pool just to make sure it wasn't a testing error and reading artificially high. Also there are no water features that would aerate my water, other than just the filter running which causes slight rippling in the surface of the water.