Steve,

You list that you have a "waterfall" in your pool. By any chance, is that waterfall being run less when you turned on your SWG? The waterfall would do a lot of aeration and cause the pH to rise. Over time, the aeration plus acid additions would cause the TA to drop and there would be less and less pH rise over time, but this would take a long time to accomplish. Was there anything else that changed, including chemical additions, the TA level, or the pH? If you turned on your SWG and found the pH to be more stable, then that is indeed out of the ordinary (based on posts from users) and would be useful to figure out.

Richard