I recently added borates to my salt water pool and as directed, I lowered my TA to 80. As expected, pH rise still occurs although more slowly with the borates. I add about 1/2 gal of 14% MA weekly to keep my pH 7.3-7.6 per Taylor 2006. My latest test results are: NaCl 3500 ppm, CH 320, Borates 50 ppm, CYA 80, TC/FC 4, pH 7.6 temp 93. I notice that as the pH trends up, I get calcium deposits on the SWG and want to maintain a constant pH.
On on my previous pool, I fashioned a CO2 delivery system for under $175 utilizing a CO2 injector from commercial pool company (check valve, injector and diffuser for $50), an old 20 lb CO2 canister from my Jeep days, and a CO2 regulator with a controllable and adjustable flow rate ($80 on a hydroponics web site). On my last pool, I infused low and slow for fixed time every night with the tank lasting about a month. I didn't have a reliable test kit with that pool, so I can't say what happened to my TA. It did keep my pH below 7.6 in a 30k gallon pool. My current pool is much smaller.
While I'm pleased with the stabilization I got with the borates, I'm contemplating rehooking up the CO2 infuser for pH control but fear that my TA will rise. Given the added difficulty of lowering them again, I am hesitant. I've seen posts repeatedly stating that TA will rise, but others state that it won't. Anyone have a definitive answer to that question or different suggestion for automated pH control?