How do I lower pH in a pool with high total alkalinity (TA)?

You can lower pH with muriatic or dry acid, but high TA (180+) will fight you. The real fix is to lower TA first: add acid to bring pH to 7.0–7.2, then aerate heavily to drive off CO₂, which raises pH but lowers TA. Repeat this cycle — acid, aerate, test — until TA drops to 80–120 ppm. Expect several rounds; it’s tedious but works.