Lowering pH without affecting TA

I'm starting up my pool and it was going pretty well. I got all the pumps going, Heater, SWGC, fountain etc. the pool is about 50000 gallons, has an automatic cleaning system, and auto cover. I raised the pH, shocked, added salt to 3200ppm and then turned to the other numbers. TA was at 60, calcium hardness was 180, CYA was 0, FC was 3.0, pH 7.4. These are all via a new Taylor DPD- FAS 2005 kit.

Here is the issue. I added 12 lbs of soda ash, in 2 doses of 6lbs each spaced out about 4 hours with everything running. This raised the TA to 120, but the pH also went up to 8. I want to lower the pH without lowering the TA. Lo-n-slow is sodium bisulfate - but that will lower the TA too... Right? Is muriatic acid better in this case? Something else?


I plan to add a little CYA, though with the pool covered 99% of the time it doesn't lose much chlorine. I can add calcium chloride to raise the calcium hardness, but that will mess with the pH too.

Any advice?

Thanks for your help.