I use bleach to chlorinate my pool, and I find that I have to add a little acid once or twice a week, as the pH rises. People in these forums have said that bleach should not be raising the pH very much, but I think in my case, it may be due to aeration, since my attached spa has a waterfall overflow into the pool. I find that my TA tends to slowly decrease (my tap water has TA of 100), so I occasionally have to add some baking soda to bring it back up, when it drops to 70 or less. I'm wondering if the aeration is causing this?
(In my old days of ignorance, when I always used a chlorinator with tri-chlor tabs, I almost never had to add acid to control pH, but my TA would tend to slowly go up over time, so I sometimes had to use acid to bring the TA down.)