The Hayward/Goldline automatic pH control, Sense and Dispense, recommends using CO2 to lower the pH. I have several questions and points to ponder on using CO2 to correct pH in pools.
1. Won't the addition of CO2 raise the TA? After all to lower the TA we are advised to aerate the water to remove CO2.
2. My pool maybe an exception, but I am adding about 16 oz of muriatic acid per week to maintain pH stable. I am using an acid pump that runs for a set time each day. I have adjusted the feed rate of the pump to the point where my pH changes less than 0.1 units per week.
3. I have been running this setup for about 6 months, and during that six months, my TA has changed from 100 to 90 ppm. This seems to indicate that my pH change is due to processes other than the loss of CO2 in the water.
It would seem that the use of CO2 to correct pH changes, over a long period of time, would result in a continuous rise in the TA.