I have seen posts on TFP saying that using bleach will usually not raise your pH, but that using tri-chlor tabs will usually lower pH (because they are so acidic) making it necessary to add pH increaser to counteract this.
My experience has been the opposite. Back when I was using Tri-Chlor tabs in an in-line chlorinator, as my main method, I found that pH stayed in the normal range 7.4 to 7.6 and that I very rarely had to add acid, and never had to add pH increaser.
Now that i am using bleach exclusively, I find that pH regularly rises, so I have to add acid a couple times a week. On average, I'm using about 1 to 1.5 gallons of 20 Baume muriatic acid per month, in a 16000 gallon pool. I'm not complaining, but am curious why my pH experience is different. The only explanation I can think of is aeration, since I've heard that tends to increase pH due to outgassing of CO2.
My pool has a waterfall from the spa with a 1 foot drop to the pool. Part of the return flow goes to the spa and part to the pool, and all the drainage is from the pool. I have a variable speed pump. I run it 10 hours a day on low speed plus 2 hours on high speed (to make my pool vac run effectively). So it gets 2 hours of fairly vigorous aeration per day.
I find that my TA is tending to go down, probably due to the regular acid dosing I have to do. My fill water has a TA of 100, and my pool TA is down to 60 now. Back when I was using tri-chlor tables and rarely added acid, I found that my TA tended to rise, and it was around 170 before I drained the pool and switched to bleach last spring.
just curious what everybody's thoughts are on this. I'm not bothered by this, other than the fact that I may have to add baking soda if the TA gets too low.